CVE-2026-42779 — mina-core
CRITICALCVE-2026-42779 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in org.apache.mina:mina-core. 1 public exploit reference exists, so weaponization risk is real. A fix is available for org.apache.mina:mina-core — see the affected versions and patch details below.
Apache MINA: AbstractIoBuffer.resolveClass() null-clazz Branch Skips acceptMatchers Filter — Full Object Deserialization RCE (take 2)
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42779.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42779 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.apache.mina:mina-core☕org.apache.mina:mina-coreReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.mina:mina-core | ≥ 2.1.0&&< 2.1.12 | 2.1.12org.apache.mina:mina-core:2.1.12 |
| ☕Maven | org.apache.mina:mina-core | ≥ 2.2.0&&< 2.2.7 | 2.2.7org.apache.mina:mina-core:2.2.7 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.mina:mina-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42779 can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat products are affected by this vulnerability. However, the vulnerable code cannot be reached and therefore are not vulnerable. Due to this reason, this flaw has been rated with a low severity.
| Product | Fixed in | Advisory |
|---|---|---|
| OpenShift Developer Tools and Services 4.12 | ocp-tools-4/jenkins-rhel8:1786628667 | RHSA-2026:60247 |
| OpenShift Developer Tools and Services 4.13 | ocp-tools-4/jenkins-rhel8:1786628681 | RHSA-2026:60249 |
| OpenShift Developer Tools and Services 4.14 | ocp-tools-4/jenkins-rhel8:1786533561 | RHSA-2026:60248 |
| OpenShift Developer Tools and Services 4.15 | ocp-tools-4/jenkins-rhel8:1786533565 | RHSA-2026:60239 |
| OpenShift Developer Tools and Services 4.16 | ocp-tools-4/jenkins-rhel9:1787125166 | RHSA-2026:60251 |
| OpenShift Developer Tools and Services 4.17 | ocp-tools-4/jenkins-rhel9:1787124635 | RHSA-2026:60246 |
| OpenShift Developer Tools and Services 4.18 | ocp-tools-4/jenkins-rhel9:1787125069 | RHSA-2026:60250 |
| OpenShift Developer Tools and Services 4.19 | ocp-tools-4/jenkins-rhel9:1787124632 | RHSA-2026:60252 |
Frequently Asked Questions
Is CVE-2026-42779 in your dependencies?
O3 Security finds CVE-2026-42779 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.