CVE-2026-107302 is a high-severity (CVSS 7.5) vulnerability in msgpack5. A fix is available for msgpack5 — see the affected versions and patch details below.
msgpack5: Truncated map32 headers throw an unexpected error
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-107302.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-107302 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
msgpack5npmDescription
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | msgpack5 | all versions | 6.1.0npm install msgpack5@6.1.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for msgpack5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update msgpack5 to 6.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-107302 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2026-107302 in your dependencies?
Find it across npm, including transitive dependencies.