{"id":"GHSA-7mv5-5mxh-qg88","summary":"nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC","details":"### Impact\nDecoding a specifically formed message can cause invalid `free()` or `realloc()` calls if the message type contains an `oneof` field, and the `oneof` directly contains both a pointer field and a non-pointer field. If the message data first contains the non-pointer field and then the pointer field, the data of the non-pointer field is incorrectly treated as if it was a pointer value. Such message data rarely occurs in normal messages, but it is a concern when untrusted data is parsed.\n\n### Patches\nPreliminary patch is available on git for [0.4.x](https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261) and [0.3.x](https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c) branches. The fix will be released in versions 0.3.9.8 and 0.4.5 once testing has been completed.\n\n### Workarounds\nFollowing workarounds are available:\n* Set the option `no_unions` for the oneof field. This will generate fields as separate instead of C union, and avoids triggering the problematic code.\n* Set the type of all fields inside the oneof to `FT_POINTER`. This ensures that the data contained inside the `union` is always a valid pointer.\n* Heap implementations that guard against invalid `free()` provide a partial mitigation. Depending on the message type, the pointer value may be attacker controlled and can be used to bypass heap protections.\n\n### References\nBug report: https://github.com/nanopb/nanopb/issues/647\n\n### For more information\nIf you have any questions or comments about this advisory, comment on the bug report linked above.","aliases":["CVE-2021-21401","PYSEC-2021-432"],"modified":"2026-07-08T06:28:07.042648156Z","published":"2024-08-30T18:45:41Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2024-08-30T18:45:41Z","nvd_published_at":"2021-03-23T18:15:00Z","cwe_ids":["CWE-763"]},"references":[{"type":"WEB","url":"https://github.com/nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21401"},{"type":"WEB","url":"https://github.com/nanopb/nanopb/issues/647"},{"type":"WEB","url":"https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c"},{"type":"WEB","url":"https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261"},{"type":"PACKAGE","url":"https://github.com/nanopb/nanopb"},{"type":"WEB","url":"https://github.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/nanopb/PYSEC-2021-432.yaml"}],"affected":[{"package":{"name":"nanopb","ecosystem":"PyPI","purl":"pkg:pypi/nanopb"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.2"},{"fixed":"0.3.9.8"}]}],"versions":["0.3.9.4.post3","0.3.9.5","0.3.9.6","0.3.9.7"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/08/GHSA-7mv5-5mxh-qg88/GHSA-7mv5-5mxh-qg88.json"}},{"package":{"name":"nanopb","ecosystem":"PyPI","purl":"pkg:pypi/nanopb"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.4.0"},{"fixed":"0.4.5"}]}],"versions":["0.4.0","0.4.1","0.4.1.dev1003","0.4.1.dev1007","0.4.1.dev1012","0.4.1.dev1013","0.4.1.dev1017","0.4.1.dev1036","0.4.1.dev959","0.4.1.dev961","0.4.1.dev962","0.4.1.dev964","0.4.1.dev971","0.4.1.dev978","0.4.1.dev980","0.4.1.dev985","0.4.1.dev987","0.4.1.dev988","0.4.1.dev996","0.4.1.dev997","0.4.2","0.4.2.dev1041","0.4.2.dev1043","0.4.2.dev1044","0.4.2.dev1045","0.4.2.dev1048","0.4.2.dev1050","0.4.2.dev1053","0.4.2.dev1054","0.4.2.dev1055","0.4.2.dev1058","0.4.2.dev1059","0.4.2.dev1063","0.4.2.dev1066","0.4.2.dev1070","0.4.2.dev1071","0.4.2.dev1072","0.4.2.dev1076","0.4.2.dev1088","0.4.2.dev1091","0.4.3","0.4.3.dev1128","0.4.3.dev1131","0.4.3.dev1132","0.4.3.dev1133","0.4.3.dev1137","0.4.3.dev1150","0.4.3.dev1164","0.4.3.dev1172","0.4.3.dev1175","0.4.3.dev1177","0.4.4","0.4.4.dev1181","0.4.4.dev1182","0.4.4.dev1184","0.4.4.dev1185","0.4.4.dev1188","0.4.4.dev1192","0.4.4.dev1193","0.4.5.dev1212","0.4.5.dev1214","0.4.5.dev1215","0.4.5.dev1217","0.4.5.dev1220","0.4.5.dev1224","0.4.5.dev1233","0.4.5.dev1234"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/08/GHSA-7mv5-5mxh-qg88/GHSA-7mv5-5mxh-qg88.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"}]}