Vulnerability · Published Jun 21, 2025 · Assigned by GitHub_M
CVE-2025-52556rfc3161-client has insufficient verification for timestamp response signatures
Critical 9.3
In plain English
A critical-severity security flaw in rfc3161-client from trailofbits. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to version 1.0.3, there is a flaw in the timestamp response signature verification logic. In particular, chain verification is performed 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. This issue has been patched in version 1.0.3. There is no workaround for this issue.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | rfc3161-client | 1.0.3 | GHSA-6qhv-4h7r-2g9m |
| PyPI | rfc3161-client | 1.0.3 | PYSEC-2026-525 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| trailofbits | rfc3161-client | < 1.0.3 |
Weakness: CWE-347 · 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