High · CVSS 7.5CVE-2026-114613

MessagePack: Unbounded memory leak in msgpack C extension on strict_map_key validation failureCVE-2026-114613

Answer in brief

CVE-2026-114613 records a High severity (CVSS 7.5) vulnerability in MessagePack: Unbounded memory leak in msgpack C extension on strict_map_key validation failure. The current sources do not mark it as known exploited. The current feed maps msgpack/msgpack-python (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 22, 2026Updated Oct 22, 2026Source checked Oct 22, 2026First seen by HOL Oct 22, 2026Material review Oct 22, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps msgpack/msgpack-python (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
msgpack/msgpack-pythongeneric	<1.2.3	1.2.3

Recommended response

Check inventory. Check lockfiles and deployed manifests for msgpack/msgpack-python.
Review the reported fix. Update msgpack/msgpack-python to 1.2.3 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 22, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.