CVE-2026-33753: CWE-295: Improper Certificate Validation in trailofbits rfc3161-client
CVE-2026-33753 is an authorization bypass vulnerability in the trailofbits rfc3161-client Python library prior to version 1. 0. 6. The flaw arises from improper certificate validation during signature verification, allowing an attacker to impersonate a trusted TimeStamping Authority (TSA). This occurs due to a logic error in extracting the leaf certificate from an unordered PKCS#7 certificate bag, enabling an attacker to append a spoofed certificate that meets the common_name and Extended Key Usage requirements. The library then incorrectly validates authorization rules against the forged certificate while verifying the cryptographic signature against a legitimate TSA certificate, bypassing TSA authorization pinning. This vulnerability is fixed in version 1. 0. 6. The CVSS score is 6.
AI Analysis
Technical Summary
The rfc3161-client Python library implements the Time-Stamp Protocol (TSP) as per RFC 3161. Versions before 1.0.6 contain a CWE-295 improper certificate validation vulnerability that allows an attacker to bypass authorization checks during signature verification. The vulnerability stems from a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates. An attacker can exploit this by appending a spoofed certificate that matches the target common_name and EKU requirements, causing the library to validate authorization rules against the forged certificate while still verifying the cryptographic signature against a trusted TSA certificate. This results in an authorization bypass, effectively allowing impersonation of a trusted TSA. The issue is resolved in version 1.0.6.
Potential Impact
An attacker exploiting this vulnerability can impersonate a trusted TimeStamping Authority by bypassing authorization checks in the rfc3161-client library. This could lead to acceptance of forged timestamps, undermining the trustworthiness of timestamped data. The vulnerability does not affect confidentiality or availability but impacts the integrity of timestamp verification.
Mitigation Recommendations
This vulnerability is fixed in rfc3161-client version 1.0.6. Users should upgrade to version 1.0.6 or later to remediate this issue. No vendor advisory is provided to indicate alternative mitigations or temporary fixes. Patch status is not explicitly confirmed beyond the fix in 1.0.6, so users should verify the upgrade and test accordingly.
CVE-2026-33753: CWE-295: Improper Certificate Validation in trailofbits rfc3161-client
Description
CVE-2026-33753 is an authorization bypass vulnerability in the trailofbits rfc3161-client Python library prior to version 1. 0. 6. The flaw arises from improper certificate validation during signature verification, allowing an attacker to impersonate a trusted TimeStamping Authority (TSA). This occurs due to a logic error in extracting the leaf certificate from an unordered PKCS#7 certificate bag, enabling an attacker to append a spoofed certificate that meets the common_name and Extended Key Usage requirements. The library then incorrectly validates authorization rules against the forged certificate while verifying the cryptographic signature against a legitimate TSA certificate, bypassing TSA authorization pinning. This vulnerability is fixed in version 1. 0. 6. The CVSS score is 6.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The rfc3161-client Python library implements the Time-Stamp Protocol (TSP) as per RFC 3161. Versions before 1.0.6 contain a CWE-295 improper certificate validation vulnerability that allows an attacker to bypass authorization checks during signature verification. The vulnerability stems from a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates. An attacker can exploit this by appending a spoofed certificate that matches the target common_name and EKU requirements, causing the library to validate authorization rules against the forged certificate while still verifying the cryptographic signature against a trusted TSA certificate. This results in an authorization bypass, effectively allowing impersonation of a trusted TSA. The issue is resolved in version 1.0.6.
Potential Impact
An attacker exploiting this vulnerability can impersonate a trusted TimeStamping Authority by bypassing authorization checks in the rfc3161-client library. This could lead to acceptance of forged timestamps, undermining the trustworthiness of timestamped data. The vulnerability does not affect confidentiality or availability but impacts the integrity of timestamp verification.
Mitigation Recommendations
This vulnerability is fixed in rfc3161-client version 1.0.6. Users should upgrade to version 1.0.6 or later to remediate this issue. No vendor advisory is provided to indicate alternative mitigations or temporary fixes. Patch status is not explicitly confirmed beyond the fix in 1.0.6, so users should verify the upgrade and test accordingly.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-23T18:30:14.125Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d672521cc7ad14da85d64f
Added to database: 4/8/2026, 3:20:50 PM
Last enriched: 4/8/2026, 3:35:59 PM
Last updated: 4/8/2026, 5:04:51 PM
Views: 4
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