rfc3161-client has insufficient verification for timestamp response signatures
Impact
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.
Patches
Users should immediately upgrade to rfc3161-client 1.0.3 or later.
Workarounds
There is no workaround possible. Users should immediately upgrade to a fixed version.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | rfc3161-client | < 1.0.3 | 1.0.3 |
References
- https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-6qhv-4h7r-2g9m
- https://nvd.nist.gov/vuln/detail/CVE-2025-52556
- https://github.com/trailofbits/rfc3161-client/commit/724a184f953e3f171f85cb223871172b41b0d0dc
- https://github.com/trailofbits/rfc3161-client
- https://pypi.org/project/rfc3161-client
- https://github.com/advisories/GHSA-6qhv-4h7r-2g9m
- CVSS vector
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- Weakness (CWE)
CWE-347- Platform
- Python (PyPI)
- Package
rfc3161-client- Disclosed
- 20.06.2025
- Updated
- 11.10.2026 14:17
Sources and licenses
OSV / GitHub Advisory Database - GHSA-6qhv-4h7r-2g9m - CC BY 4.0
OSV / GitHub Advisory Database - PYSEC-2026-525 - PyPA Advisory Database; CC BY 4.0
Vulnerability history: rfc3161-client
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 06.2025 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- Medium 1
Disclosures per year
- 2025: 1
- 2026: 1
-
rfc3161-client has insufficient verification for timestamp response signatures this entry
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