The Claude SDK for TypeScript versions 0.79.0 to before 0.81.0 contain a path traversal vulnerability in the local filesystem memory tool. The vulnerability arises because the SDK validates model-supplied paths by checking if the path string starts with a prefix matching the memory root directory, but it does not append a trailing path separator. This flaw allows a maliciously crafted path, potentially influenced by prompt injection, to resolve to a sibling directory with a name sharing the memory root's prefix, thereby escaping the sandbox restrictions. This enables unauthorized filesystem reads and writes outside the intended restricted directory. The vulnerability is tracked as CVE-2026-34451 and has a CVSS 4.0 base score of 6.3 (medium severity). The issue was patched in version 0.81.0 of the SDK.

Exploitation of this vulnerability allows an attacker to read from and write to filesystem locations outside the sandboxed memory directory intended by the SDK. This could lead to unauthorized access or modification of files on the host system where the SDK is running. The impact is limited by the requirement of a model-driven prompt injection to supply the crafted path. No known exploits are reported in the wild.

Upgrade the anthropic-sdk-typescript package to version 0.81.0 or later, where this path traversal vulnerability has been patched. No other mitigations are specified or required once the update is applied.