CVE-2025-52556: 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.
Published Jun 20, 2025 · Updated Jun 27, 2025
Affected packages
rfc3161-client
- Ecosystem
- PyPI
- Affected
- <= 1.0.2
- Fixed in
- 1.0.3
- Check
pip show rfc3161-client
Advisory details
From the GitHub Advisory Database (CC BY 4.0).
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.
Credited to jku, woodruffw.
References
How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology