CVE-2026-107302: CWE-125: Out-of-bounds Read in mcollina msgpack5
Description
### Impact A truncated `map32` header causes an out-of-bounds buffer read and throws `RangeError` instead of `IncompleteBufferError`. Applications that rely on `IncompleteBufferError` to wait for additional bytes may terminate a request, stream, or worker unexpectedly. No adjacent memory is disclosed because the buffer implementation checks bounds. ### Patches The decoder now validates the complete five-byte `map32` header before reading its length and reports truncated input as `IncompleteBufferError`. ### Workarounds Require at least five bytes before decoding a value beginning with `0xdf`, or catch `RangeError` and treat it as incomplete input only for truncated `map32` headers.
CVSS v3.1
Score 7.5high
Affected software
mcollina
msgpack5
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The msgpack5 library versions before 6.1.0 contain a flaw where the decoder reads the four-byte length of a map32 value before confirming that the entire five-byte header is present. If the header is truncated, this results in a checked out-of-bounds buffer read that throws a RangeError instead of IncompleteBufferError. Applications that expect IncompleteBufferError to handle incomplete data may terminate unexpectedly due to this error. The buffer implementation prevents adjacent memory disclosure. The issue is resolved in msgpack5 version 6.1.0.
Potential Impact
This vulnerability can cause denial of service by unexpectedly terminating requests, streams, or workers in applications using affected versions of msgpack5. There is no confidentiality or integrity impact as no adjacent memory is disclosed or corrupted. The impact is limited to availability disruption.
Mitigation Recommendations
Upgrade to msgpack5 version 6.1.0 or later, where this issue is fixed. No other mitigation is required as the vulnerability is addressed by the official patch.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-07T15:53:23.587Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ac7d49a2cdf04f6562c68aa
Added to database: 10/08/2026, 17:36:26 UTC
Last enriched: 10/08/2026, 17:48:38 UTC
Last updated: 10/08/2026, 21:48:49 UTC
Views: 7
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