CVE-2025-43521

// CVE-2025-43521 PoC - macOS Code Signing Downgrade Attack Simulation // This PoC demonstrates the concept of exploiting the downgrade vulnerability // Note: This is for educational and research purposes only #include <stdio.h> #include <stdlib.h> #include <string.h> // Simulated vulnerable code signing check int vulnerable_code_signing_check(const char* app_bundle_path) { // VULNERABLE: Only checks if app is signed, not signature freshness // In real attack, attacker provides old signed version of app FILE* f = fopen(app_bundle_path, "rb"); if (f) { // Check basic signature presence char header[4]; fread(header, 1, 4, f); fclose(f); // VULNERABLE: No version/timestamp validation if (strncmp(header, "\xfa\xde\x71\xfb", 4) == 0) { return 1; // Signed, but OLD version accepted } } return 0; } // Secure code signing check (patched version) int secure_code_signing_check(const char* app_bundle_path) { FILE* f = fopen(app_bundle_path, "rb"); if (f) { char header[4]; fread(header, 1, 4, f); fclose(f); if (strncmp(header, "\xfa\xde\x71\xfb", 4) == 0) { // ADDED: Check signature timestamp and minimum version time_t sig_time = get_signature_timestamp(app_bundle_path); time_t min_allowed = get_minimum_allowed_timestamp(); if (sig_time >= min_allowed) { return 1; // Signed and fresh enough } } } return 0; } int main(int argc, char* argv[]) { if (argc < 2) { printf("Usage: %s <app_bundle_path>\n", argv[0]); return 1; } printf("Testing vulnerable check...\n"); if (vulnerable_code_signing_check(argv[1])) { printf("[VULNERABLE] Old signed app accepted!\n"); } printf("Testing secure check...\n"); if (secure_code_signing_check(argv[1])) { printf("[SECURE] App accepted with valid signature\n"); } else { printf("[SECURE] Old signature rejected!\n"); } return 0; }

{"cve": {"id": "CVE-2025-43521", "sourceIdentifier": "[email protected]", "published": "2025-12-12T21:15:56.927", "lastModified": "2026-04-02T19:20:59.257", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "A downgrade issue affecting Intel-based Mac computers was addressed with additional code-signing restrictions. This issue is fixed in macOS Sequoia 15.7.3, macOS Tahoe 26.2. An app may be able to access sensitive user data."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-347"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*", "versionEndExcluding": "15.7.3", "matchCriteriaId": "E955E39D-E7C5-4951-BF50-08257F1BAC61"}]}]}], "references": [{"url": "https://support.apple.com/en-us/125886", "source": "[email protected]"}, {"url": "https://support.apple.com/en-us/125887", "source": "[email protected]", "tags": ["Release Notes", "Vendor Advisory"]}]}}