Menu
SUBSCRIBE
SUBSCRIBE
Menu

Project Glasswing

Anthropic CEO Dario Amodei standing before the White House, representing the company's cybersecurity collaboration with the U.S. government through Project Glasswing

U.S. Government Used Anthropic’s Mythos To Find Classified System Vulnerabilities Within Hours

, , , , , , , , , , , ,

The government participates in Project Glasswing, which gives vetted partners access to Mythos, the Anthropic model that has found more than 10,000 software vulnerabilities since April.

 

The U.S. government used Anthropic’s Mythos AI models to identify vulnerabilities in classified systems within hours, according to the Associated Press. It is the most sensitive disclosed application yet of Project Glasswing, Anthropic’s restricted program that gives vetted organizations access to its most powerful AI models to find software vulnerabilities before attackers do.

It is unclear whether the government used Mythos Preview, the original version launched in April, or Mythos 5, the latest version. The U.S. government suspended access to Mythos 5 on June 12 after citing a jailbreak identified in Fable 5, the consumer version of the same model, and halted access to both on security grounds.

Anthropic launched Project Glasswing, concurrently with Mythos, after determining that Mythos was too effective at finding vulnerabilities to release publicly. The company restricted access to a short list of vetted technology and cybersecurity companies, along with select government organizations. Partners found more than 10,000 high- and critical-severity software vulnerabilities in the program’s first weeks.

The government and Anthropic continue to work together despite the ongoing conflict between the parties. In March, the Department of Defense designated Anthropic a supply chain risk after Anthropic requested assurances its models would not be used for mass domestic surveillance or fully autonomous weapons. Anthropic challenged the designation in federal court and secured a temporary injunction. In June, the government separately ordered Anthropic to suspend access to Fable 5 and Mythos 5 due to concerns about access by foreign nationals. Anthropic complied while publicly disputing the evidence behind the order. The lawsuit remains active.

The White House held direct talks with Anthropic CEO Dario Amodei earlier this year about cybersecurity and shared AI priorities. Anthropic said it plans to expand Glasswing’s membership.

Butterfly and moth specimens forming the numeral five, cut by a red and white barrier with a stop sign, representing the suspension of Fable 5 and Mythos 5 access.

Anthropic Shuts Down Fable 5 and Mythos 5 After US Government Security Directive

, , , , , , , , , , ,

Unable to verify which customers are foreign nationals, Anthropic cut access for everyone.

 

On June 12, the US government ordered Anthropic to suspend access to Fable 5 and Mythos 5 for foreign nationals, citing national security concerns. To comply, Anthropic shut down access for all users, saying it has no mechanism to verify customer nationality.

The government says it has become aware of a jailbreak for Fable 5. Anthropic disputes the severity, calling it a non-universal jailbreak that works only in limited situations and only enables what other AI models already do freely.

Anthropic complied, but is pushing back. What the government shared, Anthropic says, constitutes a narrow, non-universal technique: one that works only under specific circumstances, not one that broadly defeats the model’s safeguards.

Anthropic said at the time of launch that no AI model can be made completely jailbreak-proof. Their stated strategy was to minimize the damage any jailbreak can cause, make them difficult to execute, and catch them quickly. The 30-day data retention requirement on Mythos-class models is part of that: it lets Anthropic review usage and shut down jailbreaks as they appear.

“If this standard was applied across the industry,” Anthropic said, “we believe it would essentially halt all new model deployments for all frontier model providers.”

 

Background

Mythos 5 and Fable 5 launched three days before the directive. Mythos 5 is available exclusively to vetted large tech companies, US and allied government organizations, and cybersecurity firms through Project Glasswing, Anthropic’s program for organizations that use AI to hunt for software vulnerabilities before attackers find them. 

Fable 5 is the consumer version of the same underlying model, with filters that detect hacking-related requests and route them to a less capable model, Opus 4.8, rather than allowing Fable 5 to respond.

Glasswing launched in April 2026 with Claude Mythos Preview, the predecessor to Mythos 5. Partners in the project identified more than 10,000 vulnerabilities using Mythos Preview, including bugs that conventional security tools had missed.

The relationship between Anthropic and the US government is strained. The US government takes an active role in vetting which organizations can access Mythos 5 through Glasswing. This cooperation exists despite an ongoing lawsuit where Anthropic sued the Department of War after the DoW designated Anthropic a supply chain risk earlier this year.

 

Anthropic says it believes the suspension is a misunderstanding and is working to restore access as soon as possible.

Butterfly and moth specimens forming the numeral five, Anthropic's launch image for Claude Mythos 5 and Claude Fable 5.

Anthropic Launches Its Next Mythos-Class Models – Claude Mythos 5, Fable 5

, , , , , , , , , , , ,

Claude Mythos 5, the latest version of Anthropic’s cyber AI model, will be released to Project Glasswing partners and later to expanded partners in consultation with the US government. 

 

Anthropic launched Claude Mythos 5, the next iteration of Claude Mythos Preview. Mythos 5 is currently available exclusively to Project Glasswing partners, with access set to expand to additional vetted organizations in partnership with the US government. 

Concurrently, Anthropic launched Claude Fable 5, a consumer version of Claude Mythos 5 with cyber safeguards in place to prevent cyber attackers from gaining access. Fable 5 doesn’t respond to potential hacker requests. Instead, it reroutes the query to a lesser model, Claude Opus 4.8. 

Like its predecessor, Mythos 5 is built to identify software vulnerabilities, analyze how they could be exploited, and help operators patch them before bad actors discover them. According to Anthropic, Claude Mythos Preview helped identify over 10,000 vulnerabilities in a few weeks, with several Glasswing partners reporting that they found more bugs faster, including those that previous methods were unlikely to find. 

Anthropic and the Federal Government 

Anthropic said in the launch statement that the US government is taking an active role in vetting who gets access to Mythos 5. Notably, the two parties continue to work together on security, despite the recent standoff between Anthropic and the White House, in which the Department of War designated Anthropic a supply chain risk. Anthropic soon countered with a lawsuit challenging the ruling. The case is still active.

Anthropic plans to expand access to Mythos 5 through a formal trusted access program for vetted cybersecurity organizations and a parallel program for biomedical researchers.

 

Abstract visualization of a dark cracked sphere with explosive blue and gold rays representing Anthropic's Project Glasswing expansion to critical infrastructure sectors.

Anthropic Expands Project Glasswing to 150 New Organizations Across 15 Countries

, , , , , , , , , , , ,

Power, water, and healthcare companies join the program as Anthropic warns that within a year, AI models will become more powerful, cheaper, and widely available, including to cybercriminals. 

 

Anthropic is extending Project Glasswing to approximately 150 new organizations in more than 15 countries, adding sectors not represented in its initial cohort, including power, water, healthcare, communications, and hardware. Each new partner must meet Anthropic’s security requirements before gaining access to Claude Mythos Preview (“Mythos”).

In April, Anthropic announced that roughly 50 initial partners, including NVIDIA, Apple, Google, Microsoft, and Amazon, had begun using Mythos to scan their codebases. Those partners found more than 10,000 high- or critical-severity security flaws in the first weeks of the program.

The new partners share one characteristic: scale of exposure. For most, Anthropic estimates a successful attack on their codebase could affect more than 100 million people, with consequences for both national and global security. Many are vendors whose software underpins systems relied on by other organizations worldwide, including governments.

Anthropic increased participation out of concern that other AI companies will likely have Mythos-class models within 6 to 12 months and could release them without safeguards that prevent misuse. In that scenario, AI-assisted cyberattacks become significantly more common and harder to predict. The company frames Project Glasswing as a way to establish operating norms before that happens.

Anthropic notes that finding vulnerabilities is no longer the bottleneck: getting them patched is. Partners now use Mythos to write patches and run pre-release checks on their own code, not just to surface problems. Anthropic says the model can also be used for penetration testing, threat detection and response, and rebuilding legacy codebases in memory-safe languages. This week, Google released AI Threat Defense, an advanced cyber detection model that also automatically applies patches.

Anthropic said it plans to further expand Glasswing, prioritizing critical infrastructure providers, open-source software maintainers, and safety testers. It is also scaling its Cyber Verification Program, which would grant Mythos-class capabilities to more organizations for specific defensive tasks. General access to Mythos, the company said, requires safeguards no AI developer has yet built.

Abstract visualization of interconnected software vulnerabilities and cyber threat detection linked to Anthropic’s Claude Mythos cybersecurity research.

Anthropic Says Its Claude Mythos Preview Identified More Than 10,000 Serious Software Vulnerabilities

, , , , , , , , , , , , , ,

Organizations participating in Anthropic’s Project Glasswing identified more than 10,000 serious software vulnerabilities using Claude Mythos Preview, including flaws participants said previous methods likely would not have found. 

 

Anthropic released a detailed update on Project Glasswing, its restricted cybersecurity initiative that gives selected organizations access to Claude Mythos Preview (Mythos) to identify software vulnerabilities in widely used technology systems before attackers can exploit them.

Participating organizations identified more than 10,000 high- and critical-severity vulnerabilities during the first weeks of the program. The company said the vulnerabilities were found in “systemically important” open-source software projects heavily used across cloud infrastructure, operating systems, browsers, enterprise applications, and internet services.

Anthropic noted that several partners are finding more bugs faster, often by a factor of 10, outpacing human-guided efforts and even previous versions of Claude. Some examples include:

  • Cloudflare identified roughly 2,000 software flaws across critical systems, including 400 classified as high or critical severity. Cloudflare said the system produced fewer incorrect vulnerability alerts than its human security testers typically generate.
  • Mozilla said it found and fixed 271 vulnerabilities in Firefox 150 after testing with Mythos. Mozilla said that was more than ten times the number of vulnerabilities identified in Firefox 148 using Claude Opus 4.6, an earlier Anthropic model.
  • The UK’s AI Security Institute said Mythos became the first AI model to successfully complete both of its simulated cyberattack exercises, meaning the system was able to carry out an entire multi-step intrusion scenario from identifying a weakness to achieving the attack objective.

 

Finding open source threats

Anthropic used Mythos to scan over 1,000 open-source software projects that support major internet systems.

The company said Mythos identified 23,019 total vulnerabilities, of which 6,202 were estimated to be high- or critical-severity.

Anthropic said 1,752 of the high- or critical-rated findings have been reviewed by six independent security research firms, with a small number reviewed by Anthropic. Of the reviewed findings, 90.6% (1,587) were confirmed as real vulnerabilities. Anthropic said 62.4%, or 1,094, were confirmed as high- or critical-severity.

Based on those review results, Anthropic said Mythos Preview is on track to identify nearly 3,900 high- or critical-severity vulnerabilities in open-source code, even if it finds no additional flaws. The company said it plans to continue scanning open-source projects, so it expects that number to increase.

The company said most vulnerabilities identified through Project Glasswing have not been publicly disclosed because software maintainers are still developing fixes. Anthropic said vulnerabilities are handled through coordinated disclosure processes, in which affected organizations receive private notice before public disclosure.

 

Anthropic introduces Cyber Verification Program, countering OpenAI’s Trusted Access for Cyber (TAC) program

Anthropic also announced a separate gated cybersecurity program for security professionals. The program removes certain cyber guardrails, allowing security professionals already using Anthropic cyber models (Mythos excepted) for cybersecurity purposes to conduct real-world research and testing.

Anthropic said it plans to expand the number of Project Glasswing partners and increase collaboration with critical partners, including governments and infrastructure operators.