CVE-2025-52556 rfc3161-client has insufficient verification for timestamp response signatures
Attackers can bypass timestamp response signature verification by providing arbitrary signatures, undermining trust in time-stamped data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-52556?
CVE-2025-52556 is a critical vulnerability in trailofbits rfc3161-client, published on 21 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-347
Which versions are affected by CVE-2025-52556?
3 open source packages ship an affected version, including rfc3161-client.
| Package | Affected | Fixed in |
|---|---|---|
rfc3161-client PyPI | All versions | 1.0.3 |
rfc3161-client PyPI | All versions | 1.0.3 |
rfc3161-client PyPI | All versions | 1.0.3 |
Linux distribution packages (1)
python-rfc3161-client openSUSE:Tumbleweed | All versions | 1.0.3-1.1 |
How do I fix CVE-2025-52556?
Upgrade rfc3161-client to 1.0.3 or later.
Is CVE-2025-52556 being exploited?
There is no known exploitation of CVE-2025-52556 in the wild and no public exploit code.
Sources
Also known as GHSA-6qhv-4h7r-2g9m, PYSEC-2026-525, openSUSE-SU-2025:15282-1.