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TI-2026-26132 Aliases CVE-2026-33753GHSA-3xxc-pwj6-jgrj

Improper Certificate Validation in rfc3161-client

Priority HIGH 66CWE-295Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Spoofing
Confidentiality · integrity · availability
None · High · None
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-295.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00195 9th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial rfc3161-client (trailofbits): 1.0.6rfc3161-client (PyPI): 1.0.6Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
trailofbitsrfc3161-clientbefore 1.0.61.0.6Patch availableCNA
—rfc3161-client (PyPI)before 1.0.61.0.6Patch availableGHSA-3xxc-pwj6-jgrj
  • rfc3161-client Vendortrailofbits Affected before 1.0.6 Fixed in 1.0.6 Patch available CNA
  • rfc3161-client (PyPI) Vendor— Affected before 1.0.6 Fixed in 1.0.6 Patch available GHSA-3xxc-pwj6-jgrj

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:trailofbits:rfc3161-client:*:*:*:*:*:*:*:*before 1.0.6Vulnerabletrailofbits
  • cpe:2.3:a:trailofbits:rfc3161-client:*:*:*:*:*:*:*:* Versions before 1.0.6 Vulnerable ·trailofbits

Remediation

  • Fix · CNA rfc3161-client (trailofbits) Fixed in 1.0.6
  • Fix · GHSA-3xxc-pwj6-jgrj rfc3161-client (PyPI) Fixed in 1.0.6 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Trusted Artifact SignerAffectedNo fix planned: Out of support scope

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-33753
  2. 2026-10-03 Alias added: GHSA-3xxc-pwj6-jgrj

References

Exploit 1

Advisory 1

Other 3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences