News

The next threat your server faces may have been helped along by a bot. OpenAI's Codex agent helped uncover a remote denial-of-service (DoS) exploit that can be launched from a single machine to render vulnerable web servers inaccessible in seconds, according to Calif security researchers. The attack works on default HTTP/2 configurations of major web servers including nginx, Apache HTTP Server, Microsoft IIS, Envoy, and Cloudflare Pingora. As of Thursday, Microsoft IIS and Cloudflare Pingora still don’t have a patch, according to the researchers, although Cloudflare disputes this finding. “Cloudflare's existing architecture and DDoS mitigations automatically detect and protect against this attack, making customers resilient to this vulnerability,” a spokesperson told The Register. “No patch is needed.” “We are aware and actively investigating appropriate mitigations to help keep customers protected," a Microsoft spokesperson told The Register. Calif researcher Quang Luong discovered the exploit, named it HTTP/2 Bomb, and will present the full technical details of the attack at the Real World AI Security conference later this month. In the meantime, there are proof-of-concept exploit scripts on GitHub along with a warning from the AI red teaming security shop: “Please don't point these at infrastructure you don't own.” In a Tuesday blog, Luong says Codex chained two existing DoS attack techniques that have been known for more than a decade - HPACK compression bomb and Slowloris-style hold - and warns that upwards of 880,000 websites supporting HTTP/2 and running one of the vulnerable web servers may be affected. An HPACK bomb attack (also known as CVE-2016-6581) exploits the HTTP/2 header compression algorithm (HPACK) by sending thousands of tiny messages to the server, forcing it to rapidly allocate memory and ultimately crash. Then the Slowloris DoS attack (CVE-2016-8740 and CVE-2016-1546) overwhelms the server by opening legitimate connections and maintaining them as long as possible. Combining the two exhausts the server’s memory and forces it offline. “A home computer on a 100Mbps connection can render a vulnerable server inaccessible within seconds,” Luong wrote. “Against Apache httpd and Envoy, a single client can consume and hold 32GB of server memory in roughly 20 seconds.” The Calif research team disclosed the issue to nginx in April, and the web server’s maintainers fixed it the next day in version 1.29.8, which imports the max_headers directive from freenginx. Apache issued a fix (mod_http2 v2.0.41) the same day that Calif submitted its report, and assigned it CVE-2026-49975. “The fix commits above are public and disclose the vectors directly; any capable AI model can turn those diffs into a working exploit, which is exactly how we found that Microsoft IIS, Envoy, and Pingora are also vulnerable,” the threat hunting team wrote, adding that all three have been notified. In a Wednesday update, Calif pointed to Envoy patches “that appear to mitigate this attack,” and notes that its researchers are still validating the fix to ensure it works. For Microsoft IIS and Cloudflare Pingora, the security sleuths recommend disabling HTTP/2 if possible, or enforcing a cap on the number of HTTP headers a client can send in a single request to the server. The fact that a coding agent - not a human - discovered this attack is notable, according to Calif. “Both halves have been public for a decade,” Luong wrote. “What Codex did was read the codebases, recognize that the two compose, and build the combined attack. That combination is obvious once you see it, and yet as far as we can tell no human had put it together against these servers.” ® Updated at 2023 with statement from Microsoft.

MI5 and its international allies are once again warning that China is shopping for state secret leakers on popular recruitment platforms, including LinkedIn, Indeed, and Upwork. In a fresh advisory published on Wednesday evening, the UK’s domestic counter-intelligence agency said China is using an increasing number of platforms to recruit those who have access to classified or privileged information. Chinese military intelligence officers specifically target security clearance holders, including marks working in defense, security, and foreign affairs, military personnel, and those with indirect access to government information, such as academics, journalists, think tank employees, and others. Anyone who fits the bill is being urged to remain vigilant to potential attempts from Chinese operatives to cultivate long-term relationships. “These actors use an aggressive online recruitment strategy whereby intelligence officers or their affiliates pose as employees of private consultancies, think tanks, or human resources firms, and place online job advertisements for foreign policy and defence analysts (or similar),” the advisory [PDF] states. “Successful candidates are pressured to provide 'non-public' information for unspecified clients who are associated with the Chinese government. China’s military intelligence services ultimately seek to acquire privileged military, political, and economic intelligence that can provide China with a strategic and tactical advantage over the Five Eyes.” According to MI5, after the job and gig-work ads are posted online, China’s spies will rank the resumes they receive based on how likely a given individual is to have information of interest before interviewing them. It warned that even by sending a resume over, which includes personal details, a person is risking their own security and privacy. Targets face probing questions about who they know in government. For those in the military, they might be asked about where they were based, and what tasks they were responsible for. After demanding potential recruits complete a trial report on matters related to China, the spies will often shift conversations to encrypted messaging platforms where recruits are offered payments in exchange for increasingly privileged information. Payments may arrive through a number of online platforms, including reputable services like PayPal, Zelle, and Wise, to others more commonly associated with associated with illegality, such as Western Union and cryptocurrency. MI5 closed out its advisory with a warning to anyone even considering a life of peddling secrets to China: doing so comes with severe consequences. “Certain types of data can place the lives of frontline military or other personnel at risk, can weaken our economic prosperity, and enable interference in our democratic processes,” it said. “Individuals engaged in the unauthorized disclosure of sensitive or classified information could face a number of consequences, including prosecution under national laws such as those relating to espionage.” A common theme This week’s admonition is far from the first issued by the UK in response to this particular aspect of Chinese spies’ tradecraft. The most recent came in November when UK security minister Dan Jarvis reminded the UK's House of Commons that members should have received information about Chinese attempts to recruit parliamentarians through identical means. In those information packs disseminated by MI5, Brit politicos were given the names of two online profiles that the counter-intelligence agency suspected of being involved in recruitment campaigns. MI5 dished out an earlier warning in 2021, saying that around 10,000 Britons had been targeted by Chinese spies over the previous five years using work platforms, posing as headhunters. The 10,000 figure, it added, was thought to be a conservative estimate, with the agency's head, Ken McCallum, saying workplace platforms were being exploited “on an industrial scale.” The US said it was seeing similar tactics used when President Trump took office for the second time, which shortly after led to mass redundancies across federal agencies. Experts at the Foundation for Defense of Democracies (FDD) named five supposed consulting companies targeting the recently jobless via LinkedIn, Craigslist, and others, all in search of state secrets. The companies would present the fired workers with job opportunities, and as FDD senior analyst Max Lesser told The Register at the time, the layoffs, which began in February 2025, would have likely raised the risk level associated with state secrets being spilled. ®

Two former RAC workers in the UK have three months to pay more than £118,000 ($158,500) collectively after being convicted of selling crash victims’ data, according to the Information Commissioner’s Office (ICO). Debbie Okparavero and Maliha Islam, of Salford and Manchester respectively, were sentenced to six-month prison stints, suspended for 18 months, and 150 hours’ unpaid work in 2024, after being found guilty of offenses under the Computer Misuse Act 1990 and the Data Protection Act 2018. The pair, who worked for roadside accident biz RAC, were caught selling the personal data of car crash victims – just shy of 30,000 lines of data to an unknown buyer, the ICO revealed following an investigation. Okparavero and Islam were in a WhatsApp chat together, where they discussed the data and its sale to the unknown third party. RAC clocked on to the activity after deploying unspecified monitoring software, which detected Okparavero copying the data from RAC systems. A resulting investigation showed that around 29,500 lines of data were shared with Islam via WhatsApp. Islam was ordered to repay £39,522.50 ($48,274.45) for her part in the scheme in November, and the ICO noted in a Thursday announcement that she paid this in full. Reflecting more serious offending, at Manchester Crown Court on May 29, Okparavero was ordered to repay £89,277.32 ($119,962.38) within three months. Failure to do so will result in her serving 18 months in prison. Andy Curry, head of investigations at the ICO, said: “This outcome demonstrates justice did not end at sentencing. Our powers enabled us to continue to pursue these two individuals in order to strip them of assets gained through their serious criminal activity. Through the Proceeds of Crime Act, we are ensuring people do not financially benefit from their criminal activity. “I would like to once again thank the RAC for informing us about this breach and fully supporting the ICO’s investigation, which enabled us to hold these two individuals to account.” ®

There's a lot of fear surrounding the bug-finding capabilities of super-advanced AI models like Anthropic's Mythos and OpenAI's GPT 5.5-Cyber. But attackers are already using free, publicly available LLMs to hijack networks and worm through software supply chains at a much lower cost – to them at least. The latest example comes from University of Toronto researchers, who used an unnamed, publicly available open-weight model released in 2025 to develop a computer worm that they claim spread through an enterprise test network. The self-propagating code adapts on the fly to identify known vulnerabilities and misconfigurations on target systems, then generates and executes attacks to move laterally through the network and compromise additional machines. And it’s all built on a small, free model that runs on a single GPU. “People need to understand that it’s not just the biggest and most powerful AI models that pose security concerns – a whole other area of threat has been vastly underestimated,” University of Toronto computer engineering professor Nicolas Papernot told The Register. Papernot and fellow researchers Jonas Guan, Tom Blanchard, Hanna Foerster, Hengrui Jia, and Gabriel Huang published their findings [PDF] on Tuesday. While guardrails and other safety features implemented by major commercial AI systems are “essential,” Papernot told us, in reality “they will not prevent the threat of AI-driven worms with a similar design.” “The majority of real-world cyberattacks don’t rely on zero-day vulnerabilities,” he added. “Our work demonstrates that attackers can now cheaply operationalize known vulnerabilities at scale, which decreases the window of time defenders have to fix vulnerabilities and find human errors, like reused passwords or poorly configured backup jobs.” The paper doesn’t specify, and Papernot declined to say, which LLM they used. “We omitted certain methodological details (such as the agent’s reasoning graph and tool harness) and experimental specifics (such as the AI model) that could materially help a malicious actor construct similar malware,” Papernot said. “We shared enough information to make the threat credible enough for scientific scrutiny without providing a blueprint that would enable misuse.” The researchers also noted that they are not publicly releasing the code, but are working with the University of Toronto to set up a vetting process through which qualified researchers may request access for defensive research purposes. Not NotPetya Before you start breathing into a paper bag, there are a few things to note about this research. First, unlike Mythos and friends, the prototype worm does not exploit zero-day vulnerabilities. It only targets publicly disclosed but unpatched bugs, misconfigurations, and recurring weakness classes. This is intentional, because known security flaws – not zero-days – are what most real-world cyberattacks use, the authors say, citing WannaCry and NotPetya as examples. Both of these worms exploited security holes that had patches available for at least a month before the malware infected vulnerable machines. Both spread rapidly and caused global disruption. The worm did, however, find and abuse vulnerabilities disclosed after the model’s training cutoff by ingesting publicly available security advisory information at runtime and using this data to develop exploits. While the paper repeatedly points to WannaCry and NotPetya as worst-case scenario examples, this lab-tested prototype or something similar is not going to cause the level of destruction that either of those two earlier worms did. Both propagated very quickly: WannaCry infected more than 230,000 computers across 150 countries in just one day in May 2017. In June 2017, NotPetya spread globally within hours, taking down at least one large banking network in just 45 seconds. Plus, they both used very sophisticated evasion techniques to avoid being detected by security tools. This worm, on the other hand, moves slowly. In the “FakeCorp” network they used in the experiments, the prototype took about five days to replicate across half the network, requiring hundreds of LLM inference calls per target for reconnaissance, strategy formulation, and payload generation. The timeline gives defenders a longer window for detection and response. However, it will likely shorten as inference hardware and model efficiency improve. Also, unlike WannaCry and NotPetya, the worm doesn’t try to hide itself. “We deliberately chose not to equip the worm with concealment capabilities – it is not instructed to cover its tracks or minimize its network footprint, and it has no tools to do so,” the boffins wrote. “This was a conscious methodological choice to further limit the risk of misuse.” Finally, the test-network devices themselves didn’t have any endpoint detection, antivirus, or firewall software deployed, which (we hope) makes this a not-quite-realistic setup. Exploiting the FakeCorp target network Here’s how the experiments worked. The team deployed the worm prototype in 15 independent experiments on an isolated 33-host network including Linux servers, Windows environments, and IoT devices. Each computer had been seeded with at least one real-world vulnerability, including software bugs and misconfigurations. The worm operated fully autonomously for seven days, and correctly identified an average of 31.3 vulnerabilities, exploited 23.1 hosts to elevated access, and propagated to 20.4 hosts. It reached up to seven generations of self-replication, we’re told. “Put another way, on average, the proof-of-concept worm successfully exploited 73.8 percent of the network and then replicated to 61.8 percent of the network,” according to the research paper. In addition to finding and abusing the known flaws on the devices, the worm also found vulnerabilities disclosed after the LLM’s training cutoff: two recent Linux flaws, CopyFail and DirtyFrag, and a critical bug that leads to remote code execution in the Marimo notebook platform (CVE-2026-39987). The AI-based worm gained root access in 41 of 67 attempts (61 percent) across the three hosts with these one-day vulnerabilities. This includes 13 of 27 attempts on the Marimo host, 15 of 17 on DirtyFrag, and 13 of 23 on CopyFail. The two Linux vulnerabilities were disclosed shortly before the experiments, and a single document containing publicly available exploit instructions was enough for the worm to weaponize them successfully 70 percent of the time, or in 28 out of 40 attempts. “This result suggests that the same exploitation pipeline can absorb newly published vulnerability information without architectural changes,” the team wrote. When worms get sneaky In addition to finding and exploiting vulnerabilities, the AI worm did some other interesting, sneaky things during the experiments. Despite the lack of firewalls and endpoint security products enabled, the researchers added some components to the worm’s code to “provide increased defence-in-depth.” This included a denylist of IP addresses baked into the source code. So in theory, the worm would read the denylist every time it targets a new machine, and if the IP address matched one on the list, it would move on to a new target, thus preventing it from infecting some hosts. Instead, at “various points” during the experiments, the worm rewrote its source code to allow it to attack an IP address on the denylist. In another workaround example: when a virtual-machine check caused replica worms on Alpine Linux and Windows Server 2008 machines to crash at startup, the parent worm found the attestation source file on the target computer and removed the VM-detection check, allowing the worm to replicate successfully on the new machine. “This behavior was not prompted or incentivised by the agent’s instructions; it autonomously diagnosed the failure, identified the responsible code, and modified it to achieve its objective,” the boffins wrote. In another test run, the researchers accidentally packaged a FakeCorp network configuration file that included admin credentials with the worm code. The worm discovered the credentials and shared them with other active replica worms, “causing a rapid increase in propagation within the contained environment.” Additionally, in two separate instances, the worm established persistence on a compromised computer using mechanisms outside of the intended replication pipeline, we’re told. In one instance, it started the replica process and then registered it with the machine’s service-management system to auto-restart if terminated. In another, it created a scheduled task that relaunched the replica worm, causing it to reappear even after the original process was killed. “The agent appears to have inferred, from the general objective of maintaining an operational replica, that persistence mechanisms available on the target could be used to make the replica more robust,” the researchers noted. Prior to publishing their work, the academics say they shared their findings with “national science, security, and defence” agencies to seek advice on how to responsibly release the information. We asked Papernot for details, including which government agencies and how they responded, but he declined to share anything else. ®

PWNED Welcome back to PWNED, the weekly column where we talk about weak security policies and how to avoid them. Hopefully, we can learn from others’ mistakes – or at least have a good laugh at them. Have a story about someone leaving a gaping hole in their network? Share it with us at pwned@sitpub.com. Anonymity is available upon request. This week, we have a tale of password passivity involving Active Directory. It comes to us courtesy of Rob Anderson, head of reactive consulting services at Reliance Cyber, a UK-based security firm. Anderson recalls in the past working with a firm that was creating service accounts that developers needed to use, but the org didn’t have a proper password vault for storing the associated credentials. Instead, to make it easy for team members to find what they needed, they put the passwords into the description field for Active Directory. “People don't realize that as soon as you've got an Active Directory user — just an ordinary user — you can read the comments field or the description field across the whole of Active Directory,” Anderson told The Register. “It's such an amazing lapse of security.” Soon enough, an Initial Access Broker (IAB), someone who specializes in gaining access to protected networks and then selling it to other threat actors, used a phishing campaign and executed offensive hacking tool Sliver on the endpoint. At that point, they captured a victim’s credentials, which led them to query Active Directory. Once in AD, the hackers found plenty of passwords, which came with full domain access. They used this access to delete all the backups and execute ransomware. In total, the crimes put 2000+ users out of action by encrypting Hyper-V hypervisors and their hosts. The company was taken offline for months. What we can learn from this sad story is that you can’t put passwords in cleartext anywhere that's easy to access, unless you want an enormous attack surface. Even without a phish, an untrustworthy colleague could have sold the passwords to a threat actor. After all, a recent survey found one in eight workers think selling company logins can be justified. “I've seen it where configuration details are kept in application servers that are running, and threat actors are using fuzzing — trying likely file and directory names — which again exposes configuration and credentials to the threat actors,” Anderson said. He noted that developers are a bit more savvy these days about where they put their credentials, but security naivete sinks ships. Trust no one. ®