msgpack5: Reserved byte can cause unbounded stream buffering

### Impact The reserved MessagePack byte `0xc1` is incorrectly treated as incomplete input. When it appears at the start of a decoder stream, all subsequent data is retained while the decoder waits for bytes that can never make the value valid, allowing memory exhaustion. ### Patches The decoder now rejects `0xc1` as invalid input. Streaming decoders release buffered input and stop after unrecoverable decoding errors. ### Workarounds Reject `0xc1` before streaming input to msgpack5, and enforce stream byte and time limits.

Source published

8 Oct 2026 17:40:01 UTC

Source modified

8 Oct 2026 18:00:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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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:N/A:H

Publisher rating · MODERATE