{"id": "GHSA-G5VF-V6WF-7W2R", "bulletinFamily": "software", "title": "Ciphertext Malleability Issue in Tink Java", "description": "### Impact\nTink's Java version before 1.5 under some circumstances allowed attackers to change the key ID part of the ciphertext, resulting in the attacker creating a second ciphertext that will decrypt to the same plaintext. This can be a problem in particular in the case of encrypting with a deterministic AEAD with a single key, and relying on the fact that there is only a single valid ciphertext per plaintext.\n\nNo loss of confidentiality or loss of plaintext integrity occurs due to this problem, only ciphertext integrity is compromised.\n\n### Patches\nThe issue was fixed in this [pull request](https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899).\n\n### Workarounds\nThe only workaround is to backport the fixing [pull request](https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899).\n\n### Details\nTink uses the first five bytes of a ciphertext for a version byte and a four byte key ID. Since each key has a well defined prefix, this extends non-malleability properties (but technically not indistinguishability). However, in the Java version this prefix lookup used a hash map indexed by unicode strings instead of the byte array, which means that invalid Unicode characters would be [replaced by U+FFFD](https://en.wikipedia.org/wiki/UTF-8#Invalid_sequences_and_error_handling) by the [Java API's default behavior](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#String(byte[],%20java.nio.charset.Charset)). This means several different values for the five bytes would result in the same hash table key, which allows an attacker to exchange one invalid byte sequence for another, creating a mutated ciphertext that still decrypts (to the same plaintext).\n\n### Acknowledgements\nWe'd like to thank Peter Esbensen for finding this issue and raising it internally.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [Tink](https://github.com/google/tink/issues)", "published": "2020-10-16T00:51:24", "modified": "2021-01-07T22:50:53", "cvss": {"score": 5.0, "vector": "AV:N/AC:L/Au:N/C:N/I:P/A:N"}, "href": "https://github.com/advisories/GHSA-g5vf-v6wf-7w2r", "reporter": "GitHub Advisory Database", "references": ["https://github.com/advisories/GHSA-g5vf-v6wf-7w2r", "https://nvd.nist.gov/vuln/detail/CVE-2020-8929", "https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r"], "cvelist": ["CVE-2020-8929"], "type": "github", "lastseen": "2021-01-08T02:26:46", "edition": 3, "viewCount": 26, "enchantments": {"dependencies": {"references": [{"type": "cve", "idList": ["CVE-2020-8929"]}, {"type": "github", "idList": ["GHSA-G5VF-V6WF-7W2R"]}], "modified": "2021-01-08T02:26:46", "rev": 2}, "score": {"value": 4.7, "vector": "NONE", "modified": "2021-01-08T02:26:46", "rev": 2}, "vulnersScore": 4.7}, "affectedSoftware": [{"name": "com.google.crypto.tink:tink", "operator": "lt", "version": "1.5.0"}], "scheme": null}

{"cve": [{"lastseen": "2020-12-09T22:03:19", "description": "A mis-handling of invalid unicode characters in the Java implementation of Tink versions prior to 1.5 allows an attacker to change the ID part of a ciphertext, which result in the creation of a second ciphertext that can decrypt to the same plaintext. This can be a problem with encrypting deterministic AEAD with a single key, and rely on a unique ciphertext-per-plaintext.", "edition": 4, "cvss3": {"exploitabilityScore": 3.9, "cvssV3": {"baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "attackComplexity": "LOW", "scope": "UNCHANGED", "attackVector": "NETWORK", "availabilityImpact": "NONE", "integrityImpact": "LOW", "baseScore": 5.3, "privilegesRequired": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "userInteraction": "NONE", "version": "3.1"}, "impactScore": 1.4}, "published": "2020-10-19T13:15:00", "title": "CVE-2020-8929", "type": "cve", "cwe": ["NVD-CWE-Other"], "bulletinFamily": "NVD", "cvss2": {"severity": "MEDIUM", "exploitabilityScore": 10.0, "obtainAllPrivilege": false, "userInteractionRequired": false, "obtainOtherPrivilege": false, "cvssV2": {"accessComplexity": "LOW", "confidentialityImpact": "NONE", "availabilityImpact": "NONE", "integrityImpact": "PARTIAL", "baseScore": 5.0, "vectorString": "AV:N/AC:L/Au:N/C:N/I:P/A:N", "version": "2.0", "accessVector": "NETWORK", "authentication": "NONE"}, "acInsufInfo": false, "impactScore": 2.9, "obtainUserPrivilege": false}, "cvelist": ["CVE-2020-8929"], "modified": "2020-10-29T22:16:00", "cpe": [], "id": "CVE-2020-8929", "href": "https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-8929", "cvss": {"score": 5.0, "vector": "AV:N/AC:L/Au:N/C:N/I:P/A:N"}, "cpe23": []}]}