CVE-2026-116580 is a high-severity (CVSS 7.3) Deserialization of Untrusted Data vulnerability in seroval. A fix is available for seroval — see the affected versions and patch details below.
Seroval: Deserialization invokes attacker-chosen callables: AsyncIteratorFactoryInstance calls source.on(listener) without type check
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-116580 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 396,966 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.
serovalnpmDescription
Summary
When fromJSON rebuilt an async iterator, it called on() on the iterator's source without checking that the source was a seroval stream. A crafted payload could pick another value as the source, such as a function returned by an application plugin. The deserializer then called that value's on method.
This is a variant of GHSA-mv8w-475r-vwqw. That fix covered the promise and stream control nodes but not the async iterator node.
Impact
An application that passes untrusted input to fromJSON with plugins that return callable values can have those callables invoked during deserialization. What this allows depends on what the plugin's values do.
Affected versions
- Versions up to 1.6.3 accept any value as the source.
- 1.6.4 rejects the reported payload.
- 1.6.5 to 1.6.7 check the source by node type, which a payload can get around by reusing a node id.
- All versions up to 1.6.7 should be treated as affected.
Patches
Fixed in [email protected]. Streams and sequences are now internal class instances. The deserializer checks the source value with instanceof, so plain data and plugin values are rejected no matter which node id they use.
Workarounds
Avoid plugins whose deserialize returns functions or objects with an on method when decoding untrusted input. Upgrading to 1.6.8 is recommended.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | seroval | all versions | 1.6.8npm install seroval@1.6.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for seroval, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update seroval to 1.6.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-116580 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
Frequently Asked Questions
Is CVE-2026-116580 in your dependencies?
Find it across npm, including transitive dependencies.