CVE-2025-13353

#!/usr/bin/env python3 """ CVE-2025-13353 PoC - gokey Seed Decryption Logic Flaw Note: This PoC demonstrates the vulnerability concept. Actual exploitation requires the seed file and understanding of gokey's key derivation. """ import struct import hashlib def simulate_weak_key_derivation(seed_file_content): """ Simulate the vulnerable key derivation in gokey < 0.2.0 Only IV (12 bytes) + Auth Tag (16 bytes) = 28 bytes used Instead of full 240 bytes seed """ # In vulnerable version, only these parts are used: # IV = first 12 bytes # Auth Tag = last 16 bytes (after AES-GCM seal) if len(seed_file_content) < 28: return None # Vulnerable: only 28 bytes extracted iv = seed_file_content[:12] auth_tag = seed_file_content[-16:] weak_entropy = iv + auth_tag # 28 bytes total # Strong: should use full 240 bytes full_entropy = seed_file_content[:240] print(f"[VULNERABLE] Entropy bytes used: {len(weak_entropy)}") print(f"[FIXED] Entropy bytes used: {len(full_entropy)}") print(f"[INFO] Entropy reduction: {(1 - 28/240)*100:.1f}%") # Derive key from weak entropy (simulating vulnerable behavior) weak_key = hashlib.sha256(weak_entropy).digest() return weak_key def main(): # Example seed file (normally 240 bytes of random data) example_seed = b'A' * 240 print("CVE-2025-13353 - gokey Seed Decryption Logic Flaw") print("=" * 60) key = simulate_weak_key_derivation(example_seed) if key: print(f"[RESULT] Weak key derived: {key.hex()}") print("[IMPACT] Attacker with seed file can brute-force 28 bytes") print("[IMPACT] Full 240 bytes entropy was intended but not used") if __name__ == "__main__": main()

{"cve": {"id": "CVE-2025-13353", "sourceIdentifier": "[email protected]", "published": "2025-12-02T11:15:47.437", "lastModified": "2025-12-15T15:31:14.013", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In gokey versions <0.2.0,\n a flaw in the seed decryption logic resulted in passwords incorrectly \nbeing derived solely from the initial vector and the AES-GCM \nauthentication tag of the key seed.\n\n\nThis issue has been fixed in gokey version 0.2.0. This is a breaking change. The fix has invalidated any passwords/secrets that were derived from the seed file (using the -s option). Even if the input seed file stays the same, version 0.2.0 gokey will generate different secrets.\n\n\nImpact\nThis vulnerability impacts generated keys/secrets using a seed file as an entropy input (using the -s option). Keys/secrets generated just from the master password (without the -s\n option) are not impacted. The confidentiality of the seed itself is \nalso not impacted (it is not required to regenerate the seed itself). \nSpecific impact includes:\n\n\n\n * keys/secrets generated from a seed file may have lower entropy: it \nwas expected that the whole seed would be used to generate keys (240 \nbytes of entropy input), where in vulnerable versions only 28 bytes was \nused\n\n * a malicious entity could have recovered all passwords, generated \nfrom a particular seed, having only the seed file in possession without \nthe knowledge of the seed master password\n\n\n\n\nPatches\nThe code logic bug has been fixed in gokey version 0.2.0\n and above. Due to the deterministic nature of gokey, fixed versions \nwill produce different passwords/secrets using seed files, as all seed \nentropy will be used now.\n\n\nSystem secret rotation guidance\nIt is advised for users to regenerate passwords/secrets using the patched version of gokey (0.2.0\n and above), and provision/rotate these secrets into respective systems \nin place of the old secret. A specific rotation procedure is \nsystem-dependent, but most common patterns are described below.\n\n\nSystems that do not require the old password/secret for rotation\nSuch systems usually have a \"Forgot password\" facility or a\n similar facility allowing users to rotate their password/secrets by \nsending a unique \"magic\" link to the user's email or phone. In such \ncases users are advised to use this facility and input the newly \ngenerated password secret, when prompted by the system.\n\n\nSystems that require the old password/secret for rotation\nSuch systems usually have a modal password rotation window\n usually in the user settings section requiring the user to input the \nold and the new password sometimes with a confirmation. To \ngenerate/recover the old password in such cases users are advised to:\n\n\n\n * temporarily download gokey version 0.1.3 https://github.com/cloudflare/gokey/releases/tag/v0.1.3 for their respective operating system to recover the old password\n\n * use gokey version 0.2.0 or above to generate the new password\n\n * populate the system provided password rotation form\n\n\n\n\nSystems that allow multiple credentials for the same account to be provisioned\nSuch systems usually require a secret or a cryptographic \nkey as a credential for access, but allow several credentials at the \nsame time. One example is SSH: a particular user may have several \nauthorized public keys configured on the SSH server for access. For such\n systems users are advised to:\n\n\n\n * generate a new secret/key/credential using gokey version 0.2.0 or above\n\n * provision the new secret/key/credential in addition to the existing credential on the system\n\n * verify that the access or required system operation is still possible with the new secret/key/credential\n\n * revoke authorization for the existing/old credential from the system\n\n\n\n\nCredit\nThis vulnerability was found by Théo Cusnir ( @mister_mime https://hackerone.com/mister_mime ) and responsibly disclosed through Cloudflare's bug bounty program."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "subAvailabilityImpact": "HIGH", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "N ... (truncated)