CVE-2026-42779: Apache MINA: AbstractIoBuffer.resolveClass() null-clazz Branch Skips acceptMatchers Filter — Full Object Deserialization RCE (take 2)
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.
Other sources
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.
— IBM
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache MINAto a version that resolves this vulnerability.Fixed in 2.1.12 - Upgrade
Upgrade
Apache MINAto a version that resolves this vulnerability.Fixed in 2.2.7
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42779?
CVE-2026-42779 is a critical vulnerability that results in full object deserialization leading to remote code execution.
What are the affected versions for CVE-2026-42779?
CVE-2026-42779 affects Apache MINA versions between 2.1.0 and 2.1.11 and between 2.2.0 and 2.2.6.
How do I fix CVE-2026-42779?
To fix CVE-2026-42779, upgrade to a patched version of Apache MINA that is above 2.1.11 or 2.2.6.
What type of attack is possible with CVE-2026-42779?
CVE-2026-42779 enables remote code execution attacks due to improper filtering in the Apache MINA library.
Is CVE-2026-42779 a known issue in earlier versions?
Yes, CVE-2026-42779 is a follow-up to CVE-2026-41635 and highlights a vulnerability that affects earlier branches of Apache MINA.