id: PYSEC-2026-525
published: "2026-06-29T11:50:38.536479Z"
modified: "2026-07-01T20:23:04.101395Z"
aliases:
- CVE-2025-52556
- GHSA-6qhv-4h7r-2g9m
summary: rfc3161-client has insufficient verification for timestamp response signatures
details: "### Impact\n\n`rfc3161-client` 1.0.2 and earlier contain a flaw in their timestamp response signature verification logic. In particular, it performs chain verification against the TSR's embedded certificates up to the trusted root(s), but fails to verify the TSR's own signature against the timestamping leaf certificates. Consequently, vulnerable versions perform insufficient signature validation to properly consider a TSR verified, as the attacker can introduce _any_ TSR signature so long as the embedded leaf chains up to some root TSA.\n\n### Patches\n\nUsers should immediately upgrade to `rfc3161-client` 1.0.3 or later.\n\n### Workarounds\n\nThere is no workaround possible. Users should immediately upgrade to a fixed version."
affected:
- package:
    name: rfc3161-client
    ecosystem: PyPI
    purl: pkg:pypi/rfc3161-client
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 1.0.3
  versions:
  - 0.0.2
  - 0.0.3
  - 0.0.4
  - 0.1.0
  - 0.1.1
  - 0.1.2
  - 1.0.0
  - 1.0.1
  - 1.0.2
references:
- type: WEB
  url: https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-6qhv-4h7r-2g9m
- type: ADVISORY
  url: https://nvd.nist.gov/vuln/detail/CVE-2025-52556
- type: WEB
  url: https://github.com/trailofbits/rfc3161-client/commit/724a184f953e3f171f85cb223871172b41b0d0dc
- type: PACKAGE
  url: https://github.com/trailofbits/rfc3161-client
- type: PACKAGE
  url: https://pypi.org/project/rfc3161-client
- type: ADVISORY
  url: https://github.com/advisories/GHSA-6qhv-4h7r-2g9m
severity:
- type: CVSS_V4
  score: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N