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CVE-2026-33753

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CVE-2026-33753

Published: Apr 8, 2026

Modified: Apr 8, 2026

PUBLISHED

CVSS v3.1

6.2

MEDIUM

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.

VendorProductVersions

trailofbits

rfc3161-client

affected
< 1.0.6

Weaknesses (CWE)

CWE-295

CVSS v3.1 Details

CVSS v3.1 Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

References

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