{"id":"PYSEC-2026-3000","summary":"pymonocypher: Potential heap buffer overflow on nb_blocks in argon2i_32 when provided buffer is too small","details":"### Impact\nThe argon2i_32 implementation does not check the nb_blocks size.  If the caller does not provide a sufficiently large buffer based on the API contract, then argon2i_32 will write past the end of the buffer and possibly corrupt the heap.\n\n### Patches\nFixed in 4.0.2.8, which now verifies that nb_blocks is large enough.  See [90ff5b1](https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86).\n\n### Workarounds\nProvide a correctly sized nb_blocks buffer.\n\npymonocypher thanks Haris (hextheshadow) for the vulnerability report, details, and recommended fix.","aliases":["CVE-2026-53720","GHSA-8f95-v3jq-cj86"],"modified":"2026-07-13T16:33:07.802709798Z","published":"2026-07-13T15:46:30.235469Z","references":[{"type":"WEB","url":"https://github.com/jetperch/pymonocypher/security/advisories/GHSA-8f95-v3jq-cj86"},{"type":"WEB","url":"https://github.com/jetperch/pymonocypher/commit/90ff5b13b13b5673c372e188f482d8c172e6ab86"},{"type":"PACKAGE","url":"https://github.com/jetperch/pymonocypher"},{"type":"PACKAGE","url":"https://pypi.org/project/pymonocypher"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-8f95-v3jq-cj86"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53720"}],"affected":[{"package":{"name":"pymonocypher","ecosystem":"PyPI","purl":"pkg:pypi/pymonocypher"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.2.8"}]}],"versions":["0.1.1","0.1.2","0.1.3","0.1.4","3.1.0.0","3.1.3.0","3.1.3.1","3.1.3.2","3.1.3.3","3.1.3.4","3.1.3.5","3.1.3.6","4.0.2.1","4.0.2.2","4.0.2.3","4.0.2.4","4.0.2.5","4.0.2.6","4.0.2.7"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/pymonocypher/PYSEC-2026-3000.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N"}]}