msgpack5: Decoding negative int64 values mutates the input buffer
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.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | msgpack5 | < 6.1.0 | 6.1.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N- Weakness (CWE)
CWE-471- Platform
- npm
- Package
msgpack5- Disclosed
- 08.10.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-qw35-55vc-rhgj - CC BY 4.0
Vulnerability history: msgpack5
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 8
- First → latest
- 03.2021 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 5
- Low 1
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 7
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msgpack5: Decoding negative int64 values mutates the input buffer this entry
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