CVE-2026-107302 msgpack5: Truncated map32 headers throw an unexpected error
A truncated map32 header in msgpack5 causes an unexpected RangeError, potentially terminating requests or workers in applications expecting incomplete buffer errors.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107302?
CVE-2026-107302 is a high-severity denial of service 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, the decoder reads the four-byte length of a map32 value before validating that the complete five-byte header is available. A truncated map32 header therefore causes a checked out-of-bounds buffer read and throws RangeError instead of IncompleteBufferError, which can unexpectedly terminate a request, stream, or worker in applications that wait for additional bytes after IncompleteBufferError. There is no adjacent-memory disclosure because the buffer implementation checks bounds. This issue is fixed in version 6.1.0.
Weakness: CWE-125
Which versions are affected by CVE-2026-107302?
2 open source packages ship an affected version, including msgpack5.
| Package | Affected | Fixed in |
|---|---|---|
msgpack5 npm | From 4.1.0 | 6.1.0 |
msgpack5 npm | From 4.1.0 | 6.1.0 |
How do I fix CVE-2026-107302?
Upgrade msgpack5 to 6.1.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-107302 being exploited?
There is no known exploitation of CVE-2026-107302 in the wild and no public exploit code.
Sources
Also known as AZL-106845, GHSA-8f34-f56x-9xph.