How severe is CVE-2026-42779?

CVE-2026-42779 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-42779?

CVE-2026-42779 affects the following packages: org.apache.mina:mina-core (Maven), org.apache.mina:mina-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-42779?

Update org.apache.mina:mina-core to 2.1.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42779 is resolved across your whole dependency graph.

How do I detect CVE-2026-42779 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.mina:mina-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-42779 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-42779?

O3 pinpoints whether CVE-2026-42779 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-42779 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42779 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-42779 published, and has it been updated?

CVE-2026-42779 was published on May 1, 2026 and was last updated on July 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

CVE-2026-42779

CRITICAL

CVE-2026-42779 is a critical-severity (CVSS 9.8) remote code execution vulnerability in org.apache.mina:mina-core. O3 Security confirms whether CVE-2026-42779 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asGHSA-vf5j-865m-mq7c

Published

May 1, 2026

Updated

Jul 15, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Real-World Exposure

2 pkgs affected

☕org.apache.mina:mina-core☕org.apache.mina:mina-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.mina:mina-core`	≥ 2.1.0&&< 2.1.12	2.1.12
☕Maven	`org.apache.mina:mina-core`	≥ 2.2.0&&< 2.2.7	2.2.7

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.mina:mina-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.apache.mina:mina-core to 2.1.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42779 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-42779 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-42779. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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.

O3 Security · Impact-Aware SCA

Is CVE-2026-42779 in your dependencies?

O3 detects CVE-2026-42779 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works