Satsuki Katayama Finance Minister issues urgent warning! Zero-day vulnerability found in the new AI "Claude Mythos" could strike directly at the financial system

What would happen if the financial system suddenly stops—have you ever imagined such a scenario? Everyone, abruptly, have you imagined a situation where an AI finds unknown security holes at speeds far surpassing human security experts and even auto-generates attack code?

It sounds like a sci-fi movie, but as of April 2026, this is becoming a real threat to the financial sector. The latest AI developed by Anthropic, Claude Mythos, is prompting cyber risks, and Finance Minister Katsuyama Satsuki is labeling it “an existing crisis now” and moving to respond urgently.

Behind the scenes, a government-private sector liaison conference involving Bank of Japan Governor, executives of the three megabanks (MUFG, SMBC, Mizuho), the Japanese Banking Association, and Japan Exchange Group (JPX) was held, just four days after the Mythos release, because the evolution of AI could swallow financial infrastructure in an instant like a “warfire.”

What do you think? Before succumbing to AI’s convenience, isn’t it necessary to properly face the risks?

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?What is the new AI “Claude Mythos”? A machine that discovers human-superior vulnerabilities

First, what kind of AI is Claude Mythos?

The latest model in the Claude series announced by Anthropic on April 7, 2026, with the official name “Claude Mythos Preview.”

Its biggest feature is an extremely high ability to rapidly discover and identify system vulnerabilities (the so-called “holes”), including OS and browsers, that humans have not been able to find before.

In benchmarks, it achieved SWE-bench Verified 93.9%, USAMO 97.6%, CyberGym 83.1%—all-time highs. In other words, it can autonomously find long-standing bugs and automatically generate practical attack code.

Tasks that would take top human experts days can be completed overnight with minimal instructions.If this capability falls into the hands of attackers... just imagining it gives you chills.

?Why cyber risks震撼 the world

If Mythos’ abilities are exploited by cyber attackers, there is concern that they could easily break through traditional security measures.

Public release has been postponed, and currently it is offered only to a select group of companies/organizations for defensive purposes under the limited “Project Glasswing (Glasswing Project).” Participants include Apple, Google, Microsoft, Amazon, CrowdStrike, JPMorgan, and potentially Japanese firms in the future.Even so, after the announcement, unauthorized access by a third party was reported, and Anthropic is investigating.

Why is it especially problematic for the financial sector? Japanese financial institutions rely heavily on legacy systems, so being exposed to unknown vulnerabilities could have significant impacts.

After the meeting, Minister Katsuyama stated to reporters, “Cyberattacks could immediately affect the market and propagate to credit concerns. It is exactly an existing crisis.”As AI advances bring warfare-like risks to finance, new preparations are needed—as the minister said, we must not underestimate the dark side of technological progress.

?Background to Finance Minister Katsuyama’s Emergency Meeting: April 24 Government-Private Top Meeting

Finance Minister Katsuyama Satsuki’s formal actions began on April 24, 2026. He held an emergency government-private joint conference with the Bank of Japan Governor, executives of the three megabanks, the Japanese Banking Association, and JPX. It was an unusually swift response, about two and a half weeks after Mythos was announced.

After the meeting, the minister emphasized, “The financial system is a critical infrastructure of the economy, so immediate action is necessary.” The reason for taking action at this timing was rapidly growing international concern.

In the United States, the Treasury and others have already held emergency meetings with major U.S. banks, and within the ruling Liberal Democratic Party in Japan, calls to strengthen countermeasures were rising. In a “now-or-never” situation, the minister herself summoned the meeting from the top down.

Everyone, when you see such swift action, doesn’t it show that politicians are seriously recognizing “an immediate crisis”??Why legacy systems in financial institutions are a trap of aging

?The aging trap of legacy systems in financial institutions

Here, let’s revisit why the financial sector is especially targeted, with a simple analogy. Modern financial transactions are supported by electronic systems that operate 24/7, but many banks still carry legacy systems that have been in use for years.Because updating to catch up with new technologies lags behind, unknown vulnerabilities are left unaddressed.

If AI like Mythos exploits this, it could construct multi-stage attack chains with minimal human intervention. As a result, if market functions pause, a loss of trust could cascade through the economy—a domino-like crisis.

Minister Katsuyama stated that new preparations are needed to defend the finance sector from the battlefield-like threats AI brings, and top management-level decisions confirmed advancing “new preparations.”Ironically, enjoying the benefits of AI while being exposed to the threats AI creates. This is the reality of 2026.

?Limited provision strategy for Project Glasswing: Anthropics Dilemma

Anthropic asserts Mythos is “the best-safety-adjusted model thus far,” while also admitting it bears “the most dangerous risks.” Therefore, they have paused general release and provide defense-only access through Project Glasswing.

Participating companies include Apple, Google, Microsoft, Amazon, CrowdStrike, JPMorgan, etc., with potential future participation by Japanese firms.

This is a strategy to “let defenders use it first and strengthen the entire industry before handing it to attackers.” In fact, the NSA is also using it for its own system vulnerability scanning.

On the other hand, unauthorized access via contractors has already occurred on the day of the announcement, and claims that time is running out are realistic. Anthropic’s decision can be seen as a responsible corporate response, but complete containment remains challenging.

? Mythos’ Threats Benchmark-Driven

Looking at Mythos’ strengths in numbers, the comparison with GPT-5.5 is interesting. Mythos 77.8% vs GPT-5.5 58.6% in SWE-bench Pro (advanced software engineering) (+19 points); Mythos 56.8–64.7% vs Humanity’s 41–52% in Last Exam (a large gap).

Especially in cyber domains (CyberGym 83.1% vs 81.8%) and practical coding, clearly one step ahead.However, in Terminal-Bench 2.0 (terminal operations), GPT-5.5 wins by a small margin, so advantages depend on use case. As Anthropic positions Mythos as a “general-purpose model,” its cyber capabilities are a byproduct of overall coding prowess.

This is the main reason for the finance minister’s caution. What do you think? The irony of AI-to-AI competition threatening human society’s safety—it is happening right before our eyes.

?Leakage risks and reality

With unauthorized access already occurring, leakage is a matter of time. Anthropic’s System Card (245 pages) notes a “step-change in vulnerability discovery,” andthey decided to proceed with limited disclosure because the abuse risk was judged to be “nuclear-weapon level.”

If development were led by states like the U.S., China, Russia, North Korea, or Iran, it could have been immediately secretive and militarized, expanding global asymmetry.

America’s hybrid strategy (limited military use + civilian defense priority) effectively affords leeway to allies including Japan. Minister Katsuyama’s ability to take countermeasures stems from information becoming public. In a sense, this is a “great response.”

However, like quantum computers, the gap between countries that have it and those that don’t will become overwhelming. How will Japan overcome this?

?Japan’s Glasswing and the necessary responses for Japan

At the conference, a decision was made to establish a government-private sector task force equivalent to a Japan-version Project Glasswing. It will discuss information sharing, strengthening vulnerability countermeasures, using defensive AI, and governance reforms. It has also been confirmed that top management-level leadership will push for “new preparations.”

This marks Japan’s first full-scale effort to build a framework against AI cyber threats. Specifics will be refined going forward, but Minister Katsuyama’s top-down stance is commendable.

If Japan wants to participate in Mythos-tier AI and share deep information with the U.S. government, a trustworthy information management system is key. Laws like the Specific Security Preservation Law, Economic Security Promotion Act, National Information Council Establishment Act, and the Spy Prevention Act currently under deliberation in this session provide the framework.

We must quickly fill the gaps that invite the label of “spy haven.” There is a lot to do.

?Threats in the AI Era

The new Claude Mythos brings cyber risks, identified by Finance Minister Satsuki Katsuyama as “an immediate crisis,” leading to an emergency joint meeting with the Bank of Japan Governor and three megabanks, and the establishment of a Japan Glasswing working group.This April 2026 event marks a turning point in financial defense in the AI era.

Anthropic’s limited provision strategy, overwhelming benchmark superiority, unauthorized access already occurring, the U.S. dilemma, and the legal and civil-military collaboration Japan needs. When you review the facts one by one, the evolution of technology brings not only convenience but alsoa “warfire” that can shake the entire economy.

Everyone, what do you think? Let’s not treat this as someone else’s problem; as depositors, investors, and as Japanese people, it’s important to watch carefully. Check the latest information from the Financial Services Agency and Anthropic official sources, and we should also be mindful of “new preparations.”

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