python-msgpack — security advisory
MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key with strict_map_key=True (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both unpackb() and the streaming Unpacker API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. This issue is fixed in version 1.2.3.
- Products
- python-msgpack
- Affected versions
- 1.0.3-2, 1.0.3-3, 1.1.2-1, 1.1.2-2, 1.1.2-3, 1.1.2-4, 1.2.1-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-114613
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 04:05 UTC · Revision 1
Source evidence
MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key with strict_map_key=True (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both unpackb() and the streaming Unpacker API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. This issue is fixed in version 1.2.3.
osv:DEBIAN-CVE-2026-114613
python-msgpack
Fixed versions: Not specified
python-msgpack
Fixed versions: Not specified
python-msgpack
Fixed versions: Not specified
Complete source record
{
"id": "7f75f97a716c3111f66259159dbc3c5aa740cff5767c8e57046b75a654ade645",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-114613",
"method": "structured",
"payload": {
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"title": "DEBIAN-CVE-2026-114613",
"summary": "MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key with strict_map_key=True (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both unpackb() and the streaming Unpacker API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. This issue is fixed in version 1.2.3.",
"evidence": "osv:DEBIAN-CVE-2026-114613",
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"modified": "2026-10-24T09:47:28.441035073Z",
"provider": "osv",
"upstream": [
"CVE-2026-114613"
],
"references": [
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"evidence": "/upstream"
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"source_id": "core-osv",
"document_id": 428972,
"published_at": "2026-10-22T19:17:37.733+00:00"
}