CVE-2025-65099
CRITICALCVE-2025-65099 is a critical-severity (CVSS 9.8) Code Injection vulnerability in anthropic claude code. O3 Security detects and blocks CVE-2025-65099 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
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…
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
claude codeanthropicDetection & mitigation playbook
Vendor / applianceDetect
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
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.