What is CVE-2026-42778?

CVE-2026-42778 is a critical-severity vulnerability in Apache Mina, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-05-01.

How severe is CVE-2026-42778?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2026-42778 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Deserialization in Apache Mina

CVE-2026-42778

The fix for CVE-2026-41409 was not applied to the 2.1.X and 2.2.X branches. Here was the original issue description: The fix for CVE-2024-52046 in Apache MINA AbstractIoBuffer.getObject() was incomplete. The classname allowlist of classes allowed to be deserialized was applied too late after a static initializer in a class to be read might already have been executed. 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 The fix for CVE-2024-52046 in Apache MINA AbstractIoBuffer.getObject() was incomplete. The classname allowlist of classes allowed to be deserialized was applied too late after a static initializer in a class to be read might already have been executed. Affected versions are Apache MINA 2.1.0 <= 2.1.110, 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

Vulnerability class: Insecure Deserialization

Published 2026-05-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (54.5th percentile), scored 2026-10-22.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.008 · change: +0.001

Affected products

Apache Mina
Apache Software Foundation Mina — versions 2.2.X, 2.1.X

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

Public proof-of-concept exploits

Akinfue/CVE-2026-42778-POC

References

lists.apache.org/thread/fhlx5k91hrkgyzh7yk1nghrn3k27gxy0 (vendor-advisory, Patch, Mailing List, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42778?: CVE-2026-42778 is a critical-severity vulnerability in Apache Mina, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-05-01.
How severe is CVE-2026-42778?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-42778 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.