Technical impact
A logic flaw in rfc3161-client's extraction of the leaf certificate from an unordered PKCS#7 bag allows an attacker to forge a certificate that matches the required common name and Extended Key Usage attributes. The library then verifies the authorization rules against the forged certificate while still validating the cryptographic signature against a legitimate trusted TimeStamping Authority. This bypasses the intended TSA authorization pinning and enables an attacker to impersonate a trusted TSA, potentially creating or claiming forged timestamps.
Affected Systems
The vulnerability affects the rfc3161-client library distributed by trailofbits. Any installation of rfc3161-client prior to version 1.0.6 is susceptible. No additional product or version specifics are provided beyond the 1.0.6 release threshold.
Risk and Exploitability
With a CVSS score of 6.2 the weakness presents a moderate severity risk. EPSS data is not available and the vulnerability is not listed in the CISA KEV catalog, indicating a lower public exploitation footprint. The attack likely requires control over the PKCS#7 signature input, allowing an attacker to inject a crafted certificate chain that satisfies the TSA verification logic. Once the forged certificate is accepted, an attacker can forge timestamps that appear valid to downstream consumers of the timestamp service.
Github GHSA