Security advisory
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-21401
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 12:37 UTC · Revision 1
Source evidence
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.
osv:CVE-2021-21401
Complete source record
{
"id": "b35e6f173d98fe6731168db04a4e10aac0a905da66e115437a319959ff99370b",
"url": "https://osv.dev/vulnerability/CVE-2021-21401",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-21401",
"summary": "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.",
"evidence": "osv:CVE-2021-21401",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-21401",
"aliases": [
"CVE-2021-21401",
"GHSA-7mv5-5mxh-qg88",
"PYSEC-2021-432"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/nanopb/nanopb",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "7ee9ef9f627d85cbe1b8c4f49a3ed26eed216c77"
},
{
"introduced": "c29ca83ff47a7224172a74ccfee07d91fa040e4c"
},
{
"fixed": "c9124132a604047d0ef97a09c0e99cd9bed2c818"
},
{
"fixed": "e2f0ccf939d9f82931d085acb6df8e9a182a4261"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:nanopb_project:nanopb:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "0.3.9.8"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:nanopb_project:nanopb:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0.4.0"
},
{
"fixed": "0.4.5"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "e2f0ccf939d9f82931d085acb6df8e9a182a4261"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"nanopb-0.3.9.7",
"0.3.9.7",
"nanopb-0.4.4",
"0.4.4",
"nanopb-0.4.3",
"0.4.3",
"nanopb-0.3.9.6",
"0.3.9.6",
"nanopb-0.4.2",
"0.4.2",
"nanopb-0.3.9.5",
"0.3.9.5",
"nanopb-0.4.1",
"0.4.1",
"nanopb-0.4.0",
"0.4.0",
"nanopb-0.3.9.4",
"0.3.9.4",
"nanopb-0.3.9.3",
"0.3.9.3",
"nanopb-0.3.9.1",
"0.3.9.1",
"nanopb-0.4.0-dev",
"nanopb-0.3.9",
"0.3.9",
"nanopb-0.3.8",
"0.3.8",
"nanopb-0.3.7",
"0.3.7",
"nanopb-0.3.6",
"0.3.6",
"nanopb-0.3.5",
"nanopb-0.3.4",
"nanopb-0.3.3",
"nanopb-0.3.2",
"nanopb-0.3.1",
"nanopb-0.2.9",
"nanopb-0.3.0",
"nanopb-0.2.8",
"nanopb-0.2.7",
"nanopb-0.2.6",
"nanopb-0.2.5",
"nanopb-0.2.4",
"nanopb-0.2.3",
"nanopb-0.2.2",
"nanopb-0.2.1",
"nanopb-0.2.0",
"nanopb-0.1.9",
"nanopb-0.1.8",
"nanopb-0.1.7",
"nanopb-0.1.6",
"nanopb-0.1.5",
"nanopb-0.1.4",
"nanopb-0.1.3",
"nanopb-0.1.2",
"nanopb-0.1.1",
"nanopb-0.1.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-21401.json",
"vanir_signatures": [
{
"id": "CVE-2021-21401-1bc41359",
"digest": {
"length": 325,
"function_hash": "135569156852612219065699278227514311302"
},
"source": "https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261",
"target": {
"file": "pb_decode.c",
"function": "pb_release_union_field"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
},
{
"id": "CVE-2021-21401-ba7b2709",
"digest": {
"threshold": 0.9,
"line_hashes": [
"61013708987579731352987091476408286170",
"327087506916403461653276454963703349803",
"44894250810108914257220512929796472898"
]
},
"source": "https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261",
"target": {
"file": "pb_decode.c"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
}
],
"vanir_signatures_modified": "2026-10-20T14:02:36Z"
}
}
],
"modified": "2026-10-20T14:02:36.261859927Z",
"provider": "osv",
"references": [
"https://github.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1",
"https://github.com/nanopb/nanopb/issues/647",
"https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261",
"https://github.com/nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88"
],
"provider_metadata": {}
},
"related_cves": [
{
"value": "CVE-2021-21401",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 388518,
"published_at": "2021-03-23T18:15:13.16+00:00"
}