Claude SDK for Python: Memory Tool Path Validation Race Condition Allows Sandbox Escape

MEDIUM 5.3CVE-2026-34452 · GHSA-w828-4qhx-vxx3 · PYSEC-2026-2115 · Published 31/03/2026 · updated 24/07/2026

In short

CVE-2026-34452 is a MEDIUM (CVSS 5.3) vulnerability affecting anthropic, claude sdk for python (anthropic).
Chance of exploitation in the next 30 days (EPSS): 0.14%, higher than 3.6% of all vulnerabilities.
Fix: update to 0.87.0 or later.

Package	Affected versions	Patched versions
anthropic PyPI	`≥ 0.86.0, < 0.87.0`	`0.87.0`
claude sdk for python anthropic	`≥ 0.86.0, < 0.87.0`	`0.87.0`

Description

The async local filesystem memory tool in the Anthropic Python SDK validated that model-supplied paths resolved inside the sandboxed memory directory, but then returned the unresolved path for subsequent file operations. A local attacker able to write to the memory directory could retarget a symlink between validation and use, causing reads or writes to escape the sandbox. The synchronous memory tool implementation was not affected.

Users on the affected versions are advised to update to the latest version.

Claude SDK for Python thanks hackerone.com/kasthelord for reporting this issue!

NVD description

The Claude SDK for Python provides access to the Claude API from Python applications. From version 0.86.0 to before version 0.87.0, the async local filesystem memory tool in the Anthropic Python SDK validated that model-supplied paths resolved inside the sandboxed memory directory, but then returned the unresolved path for subsequent file operations. A local attacker able to write to the memory directory could retarget a symlink between validation and use, causing reads or writes to escape the sandbox. The synchronous memory tool implementation was not affected. This issue has been patched in version 0.87.0.