CVE-2026-107296

Summary

msgpack5: Decoding negative int64 values mutates the input buffer

Severity

low

CVSS

3.7

EPSS

0.3% (p20)

CWE

CWE-471

Also known as

GHSA-qw35-55vc-rhgj

Published

2026-10-08

Updated

2026-10-08

Advisory details

Impact

Decoding a negative signed 64-bit integer modifies the corresponding bytes in the caller-provided input buffer. Applications that retain or reuse encoded input for integrity checks, logging, or subsequent processing may observe silently corrupted data.

Positive integers and other MessagePack value types are not affected.

Patches

The decoder now computes signed 64-bit values without writing to the input buffer.

Workarounds

Copy untrusted MessagePack input before decoding it, or do not retain or reuse input buffers after decoding.

References

• https://github.com/advisories/GHSA-qw35-55vc-rhgj
• https://github.com/mcollina/msgpack5/security/advisories/GHSA-qw35-55vc-rhgj
• https://github.com/mcollina/msgpack5/commit/82b70393a824e1088a45a377548d1d9ab82faf91
• https://github.com/mcollina/msgpack5/releases/tag/v6.1.0

Related advisories

• CVE-2026-107302 — high · npm/msgpack5
• CVE-2026-107300 — high · npm/msgpack5
• CVE-2026-107299 — medium · npm/msgpack5
• CVE-2026-107301 — medium · npm/msgpack5
• CVE-2026-107298 — medium · npm/msgpack5
• CVE-2026-107297 — medium · npm/msgpack5
• CVE-2026-92949 — medium · npm/vm2
• CVE-2026-103001 — medium · PyPI/PyJWT

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