CVE-2026-41431

#!/usr/bin/env python3 """ Conceptual PoC for CVE-2026-41431 This script simulates the vulnerable updater behavior where signature verification is skipped. In a real scenario, an attacker would serve a malicious MAR file instead of a legitimate one. """ import os def vulnerable_updater_check(mar_file_path): """ Simulates the vulnerable updater logic. It checks if the file exists but does NOT verify cryptographic signatures. """ print(f"[+] Checking for update: {mar_file_path}") if os.path.exists(mar_file_path): print("[!] Update file found.") # VULNERABILITY: Missing signature verification step # Secure code would be: if not verify_mar_signature(mar_file_path): return False print("[!] Skipping signature verification (VULNERABLE)") print("[+] Applying update...") # Simulating arbitrary code execution from the update print("[!!!] Executing unsigned code from MAR file") return True else: print("[-] No update found.") return False if __name__ == "__main__": # Simulating a malicious update file served by a compromised server malicious_mar = "malicious_update_v1.19.8.mar" # Create a dummy file to simulate existence with open(malicious_mar, 'wb') as f: f.write(b'MALICIOUS_PAYLOAD_CONTENT') print(f"--- Simulating Auto-Update Process for CVE-2026-41431 ---") result = vulnerable_updater_check(malicious_mar) if result: print("[SUCCESS] Arbitrary code executed via update mechanism.") # Cleanup os.remove(malicious_mar)

{"cve": {"id": "CVE-2026-41431", "sourceIdentifier": "[email protected]", "published": "2026-05-11T18:16:34.280", "lastModified": "2026-05-11T19:16:22.897", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "Zen is a firefox-based browser. Prior to 1.19.9b, Zen Browser ships a Mozilla Application Resource (MAR) updater (org.mozilla.updater) that has had all MAR signature verification stripped from the Firefox codebase it was forked from. The MAR files served to users contain zero cryptographic signatures, and the updater binary contains zero cryptographic verification code. This eliminates the defense-in-depth that MAR signing provides. If the update server or GitHub release pipeline is compromised, arbitrary unsigned code can be delivered to all Zen users via the auto-update mechanism. This vulnerability is fixed in 1.19.9b."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H", "baseScore": 8.0, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.3, "impactScore": 6.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-347"}]}], "references": [{"url": "https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e", "source": "[email protected]"}, {"url": "https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q", "source": "[email protected]"}, {"url": "https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}