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.

Source published

8 Oct 2026 17:39:30 UTC

Source modified

8 Oct 2026 17:45:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Publisher rating · LOW