{"id":"CVE-2021-21401","aliases":["DEBIAN-CVE-2021-21401","EUVD-2021-0139","GHSA-7mv5-5mxh-qg88","PYSEC-2021-432","UBUNTU-CVE-2021-21401","USN-6121-1","openSUSE-SU-2024:11074-1"],"status":"published","title":"Invalid free() call in Nanopb","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","severity":{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.01811,"percentile":0.78907,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":true},"cwes":["CWE-763"],"published":"2021-03-23T17:45:19Z","modified":"2026-10-23T18:03:49Z","exploits":[{"source":"pocgithub","id":"uthrasri/CVE-2021-21401_nanopb-c_AOSP10_R33","title":"uthrasri/CVE-2021-21401_nanopb-c_AOSP10_R33","date":"2024-11-05","url":"https://github.com/uthrasri/CVE-2021-21401_nanopb-c_AOSP10_R33"}],"fixes":[{"ecosystem":"PyPI","package":"nanopb","fixed_in":["0.3.9.8","0.4.5"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:12","package":"nanopb","fixed_in":["0.4.4-2"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"nanopb","fixed_in":["0.4.4-2"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"nanopb","fixed_in":["0.4.4-2"],"sources":["osv"]},{"ecosystem":"Ubuntu:Pro:20.04:LTS","package":"nanopb","fixed_in":["0.4.1-1ubuntu0.1~esm1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.2"},{"fixed":"0.3.9.8"}]}]},{"source":"ghsa","ecosystem":"PyPI","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.4.0"},{"fixed":"0.4.5"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.4-2"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.4-2"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.4-2"}]}]},{"source":"osv","ecosystem":"PyPI","package":"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"]},{"source":"osv","ecosystem":"PyPI","package":"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"]},{"source":"osv","ecosystem":"PyPI","package":"nanopb","ranges":[{"type":"GIT","events":[{"introduced":"0"},{"fixed":"e2f0ccf939d9f82931d085acb6df8e9a182a4261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.3.9.8"},{"introduced":"0.4.0"},{"fixed":"0.4.5"}]}],"versions":["0.3.9.4.post3","0.3.9.5","0.3.9.6","0.3.9.7","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"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.1-1ubuntu0.1~esm1"}]}],"versions":["0.4.1-1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.1-1ubuntu0.1~esm1"}]}],"versions":["0.4.1-1"],"bundled":2},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"nanopb","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.4.5-1.3"}]}],"bundled":3}],"products":[{"vendor":"nanopb","product":"nanopb"},{"vendor":"nanopb_project","product":"nanopb"}],"references":[{"url":"https://github.com/nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Patch","Third Party Advisory","fix","web","advisory","report"]},{"url":"https://github.com/nanopb/nanopb/issues/647","tags":["x_refsource_MISC","x_transferred","Exploit","Issue Tracking","Third Party Advisory","report","web"]},{"url":"https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://github.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1","tags":["x_refsource_MISC","x_transferred","Release Notes","Third Party Advisory","advisory","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21401","tags":["advisory"]},{"url":"https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c","tags":["web"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/nanopb/PYSEC-2021-432.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-7mv5-5mxh-qg88"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-21401","tags":["advisory"]},{"url":"https://github.com/nanopb/nanopb","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2021-21401","tags":["report"]},{"url":"https://ubuntu.com/security/notices/USN-6121-1","tags":["advisory"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-21401","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2020-26243","tags":["report"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2020-26243","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-5235","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2021-21401","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-21401","title":"Invalid free() call in Nanopb","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T17:45:19Z","modified":"2024-08-03T18:09:16.087Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high","assessor":"cna"}],"cwes":["CWE-763"],"updated_at":"2026-11-02T14:33:00.137099Z"}],"euvd":[{"id":"EUVD-2021-0139","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T17:45:19Z","modified":"2024-08-03T18:09:16Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"}],"updated_at":"2026-11-03T03:25:06.347262Z"}],"ghsa":[{"id":"GHSA-7mv5-5mxh-qg88","title":"nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC","description":"### 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.","status":"published","published":"2024-08-30T18:45:41Z","modified":"2024-08-30T18:45:42Z","cvss":[{"version":"4.0","score":7.1,"vector":"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","level":"high"},{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"}],"cwes":["CWE-763"],"updated_at":"2026-11-02T14:38:00.257632Z"}],"nvd":[{"id":"CVE-2021-21401","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T18:15:13.16Z","modified":"2026-06-17T03:35:29.647Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high","assessor":"secondary"},{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high","assessor":"primary"},{"version":"2.0","score":5.5,"vector":"AV:N/AC:L/Au:S/C:N/I:P/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-763"],"updated_at":"2026-11-02T14:06:50.805771Z"}],"osv":[{"id":"CVE-2021-21401","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T18:15:13.16Z","modified":"2026-10-20T14:02:36.261859927Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"}],"updated_at":"2026-11-02T15:44:18.004149Z"},{"id":"DEBIAN-CVE-2021-21401","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T18:15:13.16Z","modified":"2026-10-23T18:03:49.073247946Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"}],"updated_at":"2026-11-02T15:45:34.637046Z"},{"id":"GHSA-7mv5-5mxh-qg88","title":"nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC","description":"### 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.","status":"published","published":"2024-08-30T18:45:41Z","modified":"2026-07-08T06:28:07.042648156Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"},{"version":"4.0","score":7.1,"vector":"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","level":"high"}],"cwes":["CWE-763"],"updated_at":"2026-11-02T15:46:41.349637Z"},{"id":"UBUNTU-CVE-2021-21401","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T18:15:00Z","modified":"2026-04-22T12:46:44.902149Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"},{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L","level":"high"}],"updated_at":"2026-11-02T15:54:26.29421Z"},{"id":"openSUSE-SU-2024:11074-1","title":"libprotobuf-nanopb0-0.4.5-1.3 on GA media","description":"These are all security issues fixed in the libprotobuf-nanopb0-0.4.5-1.3 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2024-06-15T00:00:00Z","modified":"2026-02-04T02:52:40.75074Z","updated_at":"2026-11-02T16:58:34.894275Z"},{"id":"PYSEC-2021-432","description":"Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, decoding 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.","status":"published","published":"2021-03-23T18:15:00Z","modified":"2023-11-08T04:04:44.596402Z","updated_at":"2026-11-02T15:52:53.119977Z"},{"id":"USN-6121-1","title":"nanopb vulnerabilities","description":"It was discovered that Nanopb incorrectly handled certain decode messages.\nAn attacker could possibly use this cause a denial of service or expose\nsensitive information. (CVE-2020-26243)\n\nIt was discovered that Nanopb incorrectly handled certain decode messages.\nAn attacker could possibly use this issue to cause a denial of service\nor execute arbitrary code. (CVE-2021-21401)\n","status":"published","published":"2023-05-30T16:09:29Z","modified":"2026-04-22T10:35:16.428853Z","updated_at":"2026-11-02T16:58:16.738762Z"}]}}