{"cve":"CVE-2026-33753","nvd":{"published":"2026-04-08T16:16:23.670","modified":"2026-07-24T23:10:00.563","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5},"cwes":["CWE-295"],"references":["https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj","https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj"],"products":["trailofbits:rfc3161-client"],"source":"nvd","synced_at":"2026-10-19T22:28:59.047572785+00:00"},"epss":{"cve":"CVE-2026-33753","score":0.00188,"percentile":0.08398,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-3xxc-pwj6-jgrj","url":"https://osv.dev/vulnerability/GHSA-3xxc-pwj6-jgrj","summary":"rfc3161-client Has Improper Certificate Validation","modified":"2026-07-13T16:43:08.687187641Z","packages":[{"ecosystem":"PyPI","name":"rfc3161-client","purl":"pkg:pypi/rfc3161-client","ranges":["<1.0.6"],"fixed":["1.0.6"]}]},{"id":"PYSEC-2026-3051","url":"https://osv.dev/vulnerability/PYSEC-2026-3051","summary":"rfc3161-client Has Improper Certificate Validation","modified":"2026-07-13T16:32:43.974659362Z","packages":[{"ecosystem":"PyPI","name":"rfc3161-client","purl":"pkg:pypi/rfc3161-client","ranges":["<1.0.6"],"fixed":["1.0.6"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}