GPT-5.5 matches Mythos in cybersecurity tests, challenging Anthropic's restricted release
15 Sources
[1]
Amid Mythos' hyped cybersecurity prowess, researchers find GPT-5.5 is just as good
Last month, Anthropic made a big deal about the supposedly outsized cybersecurity threat represented by its Mythos Preview model, leading the company to restrict the initial release to "critical industry partners." But new research from the UK's AI Security Institute (AISI) suggests that OpenAI's
[2]
OpenAI's new security model is for 'critical cyber defenders' only
It's not clear who will get access to the model first, though previous "trusted access" schemes involved vetted professionals and institutions. Details of the model and its capabilities are also unclear; OpenAI has not released any technical details or specifications. The name indicates it is a
[3]
Mythos AI is a cybersecurity threat, but it doesn't rewrite the rules of the game
The cybersecurity community went on alert when Anthropic announced on April 7, 2026, that its latest and most capable general-purpose large language model, Claude Mythos Preview, had demonstrated remarkable - and unintended - capabilities. The artifical intelligence system was able to find and
[4]
Anthropic Mythos shaping up as nothingburger
Anthropic's Mythos model is purportedly so good at finding vulnerabilities that the Claude-maker is afraid to make it available to the general public for fear that criminals will take advantage. But early analysis shows that Mythos may not be as dangerous as some would have you believe. Anthropic
[5]
Anthropic CEO warns of cyber 'moment of danger' as AI exposes thousands of vulnerabilities
Denis Balibouse | Reuters | Samuel Corum | Bloomberg | Getty Images Anthropic CEO Dario Amodei warned Tuesday that artificial intelligence has created a narrow window for the world's tech firms, governments and banks to fix tens of thousands of software vulnerabilities found by his company's
[6]
OpenAI locks GPT-5.5-Cyber behind velvet rope
Altman's crew now doing the same gatekeeping it recently mocked OpenAI is lining up a limited release of its new GPT-5.5-Cyber model to a handpicked circle of "cyber defenders," just weeks after taking a swipe at Anthropic for doing almost exactly the same thing. CEO Sam Altman said in a post on
[7]
OpenAI isn't far behind Mythos' hacking powers
Why it matters: The head start that cyber defenders were promised when Mythos was unveiled last month is disappearing faster than expected. Driving the news: The U.K. AI Security Institute said Thursday that GPT-5.5 was able to complete a 32-step simulated corporate cyberattack in 2 out of 10 test
[8]
'Moment of Danger': Anthropic CEO Warns of Cyber Risk Window as AI Uncovers Software Flaws - Decrypt
Critics say the risks may be overstated even as security concerns grow. A discussion between Anthropic CEO Dario Amodei and JPMorgan Chase CEO Jamie Dimon on Tuesday focused on the growing cybersecurity threat posed by artificial intelligence as it identifies vulnerabilities faster than
[9]
Mythos AI may be a cybersecurity threat, but it follows the rules of the game
The news ignited concern among the public, world governments, and the information technology sector about the capabilities of today's AI to undermine cybersecurity, with some people framing the model as a global cybersecurity threat. Claiming that it would be too risky to release the model, and
[10]
OpenAI's GPT-5.5 Matches Claude Mythos in Cyberattack Capabilities: AI Security Institute - Decrypt
Researchers found a jailbreak that bypassed GPT-5.5's safety guardrails entirely, raising alarms. A U.K. government agency has found that OpenAI's newest artificial intelligence model can autonomously carry out complex cyberattacks -- and that it cracked a reverse-engineering challenge in just
[11]
Mythos has business worried. The rest are lulled into false cybersecurity
This is the everyday reality of the technology that runs much of Australia is not well-defended. Health systems. Water utilities. Thousands of others. A few weeks ago in these pages I wrote that we had crossed the Rubicon on cyber risk: that the threshold between human-paced attack and
[12]
OpenAI expands Trusted Access program with GPT-5.5-Cyber
OpenAI has begun the rollout of GPT-5.5-Cyber, an AI model focused on cybersecurity, aiming to deliver it to "critical cyber defenders" within days. This initiative follows Anthropic's announcement of Claude Mythos Preview, a model found to autonomously discover numerous software vulnerabilities,
[13]
OpenAI Confirms GPT-5.5 Cyber Model's Rollout Is Around the Corner
The new model comes less than a month after GPT-5.4 Cyber's release OpenAI CEO Sam Altman teased the successor to the GPT-5.4 Cyber artificial intelligence (AI) model on Thursday. Dubbed GPT-5.5 Cyber, the model was announced just a fortnight after the San Francisco-based AI giant introduced its
[14]
Anthropic CEO Predicts Firms Have 6 Months to Patch Software Vulnerabilities | PYMNTS.com
By completing this form, you agree to receive marketing communications from PYMNTS and to the sharing of your information with our sponsor, if applicable, in accordance with our Privacy Policy and Terms and Conditions. Speaking during Anthropic's livestreamed event The Briefing: Financial
[15]
OpenAI Will Arm Critical Cyber Defenders With Frontier Model | PYMNTS.com
By completing this form, you agree to receive marketing communications from PYMNTS and to the sharing of your information with our sponsor, if applicable, in accordance with our Privacy Policy and Terms and Conditions. "We will work with the entire ecosystem and the government to figure out
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OpenAI's publicly released GPT-5.5 performed just as well as Anthropic's restricted Mythos model on cybersecurity evaluations, achieving 71.4% success on expert-level tasks. The UK's AI Security Institute found both models succeeded at previously impossible network penetration tests, raising questions about whether Mythos warranted its limited release amid accusations of fear-based marketing.
GPT-5.5 Achieves Similar Cybersecurity Performance as Mythos
New research from the UK's AI Security Institute (AISI) reveals that OpenAI's GPT-5.5, which launched publicly last week, reached "a similar level of performance on our cyber evaluations" as Anthropic's heavily restricted Mythos Preview model
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. On expert-level Capture the Flag challenges designed to test capabilities in reverse engineering, web exploitation, and cryptography, GPT-5.5 passed an average of 71.4 percent of tasks, slightly higher than the 68.6 percent achieved by Mythos Preview, though within the margin of error1
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Source: Gadgets 360
The AISI has tested frontier AI models through 95 different challenges since 2023, and both GPT-5.5 and Mythos demonstrated unprecedented success on "The Last Ones" simulation, which mimics a 32-step data extraction attack on a corporate network. GPT-5.5 succeeded in 3 of 10 attempts compared to Mythos Preview's 2 of 10—no previous model had ever succeeded even once
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. In one particularly difficult task involving building a disassembler to decode a Rust binary, GPT-5.5 solved the challenge in 10 minutes and 22 seconds with no human assistance at a cost of $1.73 in API calls1
.Questions About Anthropic's Restricted Release Strategy
The comparable performance raises significant questions about whether Mythos warranted its restricted release through Project Glasswing, which granted exclusive access to select tech giants
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. Anthropic claimed in April that Mythos represented such a severe cybersecurity threat that immediate public release would be too risky3
. However, AISI's findings suggest Mythos was likely not "a breakthrough specific to one model" but rather "a byproduct of more general improvements in long-horizon autonomy, reasoning, and coding"1
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Source: The Register
OpenAI CEO Sam Altman criticized what he calls fear-based marketing in promoting limited AI model releases. While acknowledging Mythos is "a great model for cybersecurity," Altman told the Core Memory podcast that "it is clearly incredible marketing to say, 'We have built a bomb. We are about to drop it on your head. We will sell you a bomb shelter for $100 million'"
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. He predicted there will be "a lot more rhetoric about models that are too dangerous to release," while acknowledging that truly dangerous models will require controlled release programs1
.Reality Check on Finding Software Vulnerabilities
Early reports from Mythos preview users including AWS and Mozilla indicate that while the model excels at finding software vulnerabilities quickly and requires less hands-on guidance from security engineers, it hasn't eclipsed elite human security researchers
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. Mozilla CTO Bobby Holley revealed that Mythos found 271 vulnerabilities in Firefox 150, noting "So far we've found no category or complexity of vulnerability that humans can find that this model can't," but added crucially: "We also haven't seen any bugs that couldn't have been found by an elite human researcher"4
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Source: PYMNTS
Cybersecurity researchers emphasize that Mythos didn't discover fundamentally new classes of software vulnerabilities. The vulnerabilities are generally variations of well-known and well-understood security flaws
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. What concerned researchers was the intense scale and speed with which Mythos could find and exploit those vulnerabilities, not a fundamental change in the nature of the cybersecurity threat3
.Related Stories
OpenAI Follows Controlled Release Approach
Despite Altman's criticism, OpenAI is adopting similar controlled release programs for its own cybersecurity-focused models. In February, OpenAI rolled out its Trusted Access for Cyber pilot program, allowing security researchers and enterprises to verify their identities and register interest in studying frontier models for "legitimate defensive work"
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. Last month, the company used this list to control the limited launch of GPT-5.4-Cyber, a model variant "purposely fine-tuned for additional cyber capabilities and with fewer capability restrictions"1
.On Thursday, Altman announced that GPT-5.5-Cyber would similarly be limited "to critical cyber defenders in the next few days," though details about who qualifies as "critical cyber defenders" and the model's specific capabilities remain unclear
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. This staggered rollout represents a growing trend in the AI industry of companies branding their top models too dangerous for public release due to potential misuse by criminals2
.Security Concerns and Geopolitical Implications
Anthropic CEO Dario Amodei warned that AI has created a narrow window for tech firms, governments, and banks to fix tens of thousands of software vulnerabilities found by Mythos. Since AI models from geopolitical adversaries like China are "maybe six to 12 months" behind Anthropic's product, there is "roughly that amount of time" to address these issues before potential misuse by criminals becomes a more serious concern
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. Amodei noted that the scale of potential cyber exploits has ballooned with each generation of Claude, with an earlier model finding roughly 20 vulnerabilities in Firefox while Mythos found nearly 300, bringing the total count across all software into the tens of thousands5
.References
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