CVEvulnerability

CVE-2026-33753

7.5 HIGH Published 2026-04-08 Modified 2026-07-24 Official page ↗
Status
Analyzed
Published
2026-04-08
Last modified
2026-07-24
Assigner
[email protected]
CVSS 3.1 ([email protected])
6.2 MEDIUM — CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weaknesses
CWE-295

Description

rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates, an attacker can append a spoofed certificate matching the target common_name and Extended Key Usage (EKU) requirements. This tricks the library into verifying these authorization rules against the forged certificate while validating the cryptographic signature against an actual trusted TSA (such as FreeTSA), thereby bypassing the intended TSA authorization pinning entirely. This vulnerability is fixed in 1.0.6.

Affected configurations

• trailofbits rfc3161-client (< 1.0.6)

Related

Weakness · CWE (1)

  • CWE-295 Improper Certificate Validation weakness

References