{"id":"PYSEC-2026-525","summary":"rfc3161-client has insufficient verification for timestamp response signatures","details":"### Impact\n\n`rfc3161-client` 1.0.2 and earlier contain a flaw in their timestamp response signature verification logic. In particular, it performs chain verification against the TSR's embedded certificates up to the trusted root(s), but fails to verify the TSR's own signature against the timestamping leaf certificates. Consequently, vulnerable versions perform insufficient signature validation to properly consider a TSR verified, as the attacker can introduce _any_ TSR signature so long as the embedded leaf chains up to some root TSA.\n\n### Patches\n\nUsers should immediately upgrade to `rfc3161-client` 1.0.3 or later.\n\n### Workarounds\n\nThere is no workaround possible. Users should immediately upgrade to a fixed version.","aliases":["CVE-2025-52556","GHSA-6qhv-4h7r-2g9m"],"modified":"2026-07-13T16:15:34.044532111Z","published":"2026-06-29T11:50:38.536479Z","references":[{"type":"WEB","url":"https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-6qhv-4h7r-2g9m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-52556"},{"type":"WEB","url":"https://github.com/trailofbits/rfc3161-client/commit/724a184f953e3f171f85cb223871172b41b0d0dc"},{"type":"PACKAGE","url":"https://github.com/trailofbits/rfc3161-client"},{"type":"PACKAGE","url":"https://pypi.org/project/rfc3161-client"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-6qhv-4h7r-2g9m"}],"affected":[{"package":{"name":"rfc3161-client","ecosystem":"PyPI","purl":"pkg:pypi/rfc3161-client"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.0.3"}]}],"versions":["0.0.2","0.0.3","0.0.4","0.1.0","0.1.1","0.1.2","1.0.0","1.0.1","1.0.2"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/rfc3161-client/PYSEC-2026-525.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}