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Advisory record · GHSA-6qhv-4h7r-2g9m

rfc3161-client has insufficient verification for timestamp response signatures

CVSS 9.3 CriticalCriticalEPSS 0.0017 · 6th percentile

Critical, because:

  • CVSS score 9.3: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 29 Jun 2026, 11:50 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
rfc3161-clientPyPI<1.0.31.0.3
Identifiers
GHSA-6qhv-4h7r-2g9m · CVE-2025-52556 · PYSEC-2026-525
Weakness (CWE)
CWE-347
Tags
Published
29 Jun 2026
Updated
13 Jul 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

rfc3161-client versions before 1.0.3 do not fully verify timestamp response (TSR) signatures. The library checks the embedded certificate chain up to a trusted root but does not check the TSR's own signature against the leaf certificate, so an attacker can supply an arbitrary signature alongside a valid chain and have the response accepted. Upgrade to rfc3161-client 1.0.3 or later; the source lists no workaround.

Written 6 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.3 Critical 4.0 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 CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0017, the 6th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 15:04 UTC First seen by agentprime
  2. 31 Oct 2026, 15:04 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.