June 24, 2026, (Inside AI) — Anthropic’s advanced AI model Mythos uncovered critical security weaknesses in classified U.S. government systems during a recent testing program, according to a new report. The Associated Press, citing an unnamed U.S. official speaking on condition of anonymity, revealed the model found the flaws as part of a restricted initiative called Project Glasswing.
Project Glasswing brought together tech giants and other companies to secure critical software. The official described the effort as guarding against severe fallout to public safety, national security, and the economy. The goal was to find and fix vulnerabilities before criminals or foreign adversaries could exploit them.
At a June 11 Senate Banking Committee session, Senator Mark Warner of Virginia referenced the testing. He said the tool broke into almost all classified systems, not in weeks but in hours. Warner attributed that account to General Joshua Rudd, who heads the NSA and U.S. Cyber Command.
“Encryption was a potent technology, but narrow in its application. AI is far more powerful and versatile. On June 11th Mark Warner, the vice-chair of the Senate Intelligence Committee, said that General Joshua Rudd, who leads the National Security Agency and the Pentagon’s Cyber Command, had told him that Mythos ‘broke into almost all of our classified systems, not in weeks, but in hours’,” reported The Economist.
Vulnerability Discovery Versus Real-World Exploitation
The unnamed official offered an important caveat: finding vulnerabilities is not the same as exploiting them. Mythos identified weak points quickly, but no evidence shows it seized control. The distinction matters for judging real-world risk. The NSA declined to comment, and an Anthropic spokesman did the same. The White House and Defense Department did not immediately respond, leaving the account largely unconfirmed on the record.
The story lands amid rising tension between Anthropic and the government. The company has raised concerns over how the U.S. military would use its AI. In response, the administration restricted access to some Anthropic models. Earlier this month, a directive required Anthropic to block foreign nationals from using Fable 5 and Mythos 5. The company disabled both models for all customers to comply, stating it did not believe the action was warranted by the concern raised.
Fable is a limited version of the more powerful Mythos. Anthropic tightly restricted Mythos access due to its cybersecurity capabilities, while Fable was released more widely earlier this month. The directive came 10 days after President Donald Trump signed an executive order establishing a framework to vet national security risks of advanced AI before public release. The government can now review the most capable systems for up to a month.
Industry Pushback and National Security Implications
Industry voices pushed back hard on the crackdown. More than 100 cybersecurity experts signed a letter urging a reversal. Signatories included leaders from Adobe and NVIDIA. They called Mythos quite good at finding and weaponizing software flaws but stressed it is not uniquely good at those tasks. Many said they use other foundation and open-source models for security work. The letter warned against removing strong cyber defense tools without good reason, arguing it could help U.S. adversaries more than it protects against them.
Reports also suggest the NSA may have lost access to Mythos during the dispute. The episode underscores AI’s growing role in national security and cyber defense. As tensions persist, the balance between innovation and security remains a critical challenge for policymakers and industry leaders alike.
