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Fencer Vulns
medium 5.3

CVE-2026-34452 json

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

published 2026-03-31 7 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-17681 , GHSA-w828-4qhx-vxx3 , PYSEC-2026-2115

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi anthropic 0.87.0
  • anthropic anthropic 0.87.0
  • anthropic claude_sdk_for_python 0.87.0

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 5.8 CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
GitHub 3.1 5.3 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
CNA 4.0 5.8 CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.3 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
OSV 3.1 5.3 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi anthropic
>=0.86.0, <0.87.0
0.87.0

Affected products

  • anthropics anthropic-sdk-python

Classification

Weakness
  • CWE-59 Improper Link Resolution Before File Access
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.