CVE-2026-33753 | trailofbits rfc3161-client up to 1.0.5 Time-Stamp Protocol certificate validation

VDB-356264 · CVE-2026-33753 · GCVE-0-2026-33753 TRAILOFBITS RFC3161-CLIENT UP TO 1.0.5 TIME-STAMP PROTOCOL CERTIFICATE VALIDATION HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 4.5 $0-$5k 0.25+ Summaryinfo A vulnerability was found in trailofbits rfc3161-client up to 1.0.5. It has been declared as critical. The impacted element is an unknown function of the component Time-Stamp Protocol Handler. Such manipulation leads to certificate validation. This vulnerability is traded as CVE-2026-33753. An attack has to be approached locally. There is no exploit available. It is recommended to upgrade the affected component. Detailsinfo A vulnerability was found in trailofbits rfc3161-client up to 1.0.5. It has been rated as problematic. Affected by this issue is some unknown processing of the component Time-Stamp Protocol Handler. The manipulation with an unknown input leads to a certificate validation vulnerability. Using CWE to declare the problem leads to CWE-295. The product does not validate, or incorrectly validates, a certificate. Impacted is integrity. CVE summarizes: 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. The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-33753 since 03/23/2026. The exploitation is known to be difficult. The attack needs to be approached locally. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1587.003. Upgrading to version 1.0.6 eliminates this vulnerability. Productinfo Type Application Server Software Vendor trailofbits Name rfc3161-client Version 1.0.0 1.0.1 1.0.2 1.0.3 1.0.4 1.0.5 Website Product: https://github.com/trailofbits/rfc3161-client/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 4.5 VulDB Meta Temp Score: 4.5 VulDB Base Score: 2.9 VulDB Temp Score: 2.8 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 6.2 CNA Vector (GitHub_M): 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Certificate validation CWE: CWE-295 / CWE-287 CAPEC: 🔒 ATT&CK: 🔒 Physical: Partially Local: Yes Remote: No Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: rfc3161-client 1.0.6 Timelineinfo 03/23/2026 CVE reserved 04/08/2026 +15 days Advisory disclosed 04/08/2026 +0 days VulDB entry created 04/08/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: github.com Status: Confirmed CVE: CVE-2026-33753 (🔒) GCVE (CVE): GCVE-0-2026-33753 GCVE (VulDB): GCVE-100-356264 Entryinfo Created: 04/08/2026 17:58 Changes: 04/08/2026 17:58 (65) Complete: 🔍 Cache ID: 99:8F2:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸