CVE-2026-107296 msgpack5: Decoding negative int64 values mutates the input buffer
Decoding negative int64 values in msgpack5 mutates the input buffer, causing silent data corruption for applications reusing the buffer.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107296?
CVE-2026-107296 is a low-severity vulnerability in mcollina msgpack5, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, decoding a negative signed 64-bit integer modifies the corresponding bytes in the caller-provided input buffer while computing the value. Applications that retain or reuse encoded input for integrity checks, logging, or later processing can observe silently corrupted data, while positive integers and other MessagePack value types are unaffected. This issue is fixed in version 6.1.0.
Weakness: CWE-471
Which versions are affected by CVE-2026-107296?
2 open source packages ship an affected version, including msgpack5.
| Package | Affected | Fixed in |
|---|---|---|
msgpack5 npm | All versions | 6.1.0 |
msgpack5 npm | All versions | 6.1.0 |
How do I fix CVE-2026-107296?
Upgrade msgpack5 to 6.1.0 or later.
Is CVE-2026-107296 being exploited?
There is no known exploitation of CVE-2026-107296 in the wild and no public exploit code.
Sources
Also known as AZL-106854, GHSA-qw35-55vc-rhgj.