How severe is CVE-2025-65099?

CVE-2025-65099 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which products are affected by CVE-2025-65099?

Affected package information for CVE-2025-65099 is not yet fully mapped. Check the official advisory links for details.

How do I patch CVE-2025-65099?

Apply the anthropic claude code security patch or hotfix for CVE-2025-65099 on the affected version, following the vendor advisory for your exact build.

How do I detect CVE-2025-65099 across my infrastructure?

Inventory every anthropic claude code deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

How do I mitigate CVE-2025-65099 if there is no patch (or I can't update yet)?

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2025-65099?

O3 detects and blocks CVE-2025-65099 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Is CVE-2025-65099 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-65099 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-65099?

CVE-2025-65099 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 35th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-65099?

CVE-2025-65099 is classified as Code Injection (CWE-94). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2025-65099?

CVE-2025-65099 affects anthropic claude code. Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2025-65099 published, and has it been updated?

CVE-2025-65099 was published on November 19, 2025 and was last updated on June 17, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2025-65099: Claude Code Code Injection (Critical 9.8)

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk35th percentile+0.35%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

Claude Code is an agentic coding tool. Prior to version 1.0.39, when running on a machine with Yarn 3.0 or above, Claude Code could have been tricked to execute code contained in a project via yarn plugins before the user accepted the startup trust dialog. Exploiting this would have required a user to start Claude Code in an untrusted directory and to be using Yarn 3.0 or above. This issue has been patched in version 1.0.39.

Affected Products

1 product · 1 configurations

Application

claude codeanthropic

< 1.0.39

range

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every anthropic claude code deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the anthropic claude code security patch or hotfix for CVE-2025-65099 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2025-65099 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2025-65099. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Claude Code is an agentic coding tool. Prior to version 1.0.39, when running on a machine with Yarn 3.0 or above, Claude Code could have been tricked to execute code contained in a project via yarn plugins before the user accepted the startup trust dialog. Exploiting this would have required a user to start Claude Code in an untrusted directory and to be using Yarn 3.0 or above. This issue has been patched in version 1.0.39.

O3 Security · Runtime Protection

Is CVE-2025-65099 being exploited in your environment?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2025-65099 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.

Protect my workloads How runtime protection works

CVE-2025-65099

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is CVE-2025-65099 being exploited in your environment?