CVE-2025-52556
rfc3161-client has insufficient verification for timestamp response signatures
Description
### 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.
How to fix CVE-2025-52556
To remediate CVE-2025-52556, upgrade the affected package to a fixed version below.
- —upgrade to 1.0.3 or later
Is CVE-2025-52556 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 1.0.3
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 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 |