CVE-2023-42811: AEADs/aes-gcm Plaintext Exposed Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-423w-p2w9-r7vq",
  "modified" : "2025-12-31T22:00:24Z",
  "published" : "2023-09-22T16:11:47Z",
  "aliases" : [ "CVE-2023-42811" ],
  "summary" : "AEADs/aes-gcm: Plaintext exposed in decrypt_in_place_detached even on tag verification failure",
  "details" : "### Summary\nIn the AES GCM implementation of decrypt_in_place_detached, the decrypted ciphertext (i.e. the correct plaintext) is exposed even if tag verification fails. \n\n### Impact\nIf a program using the `aes-gcm` crate's `decrypt_in_place*` APIs accesses the buffer after decryption failure, it will contain a decryption of an unauthenticated input. Depending on the specific nature of the program this may enable Chosen Ciphertext Attacks (CCAs) which can cause a catastrophic breakage of the cipher including full plaintext recovery.\n\n### Details\nAs seen in the implementation of [decrypt_in_place_detached](https://docs.rs/aes-gcm/latest/src/aes_gcm/lib.rs.html#309) for AES GCM, if the tag verification fails, an error is returned. Because the decryption of the ciphertext is done in place, the plaintext contents are now exposed via `buffer`. \n\nThis should ideally not be the case - as noted in page 17 of[ NIST's publication _Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC_](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf): \n_In Step 8, the result of Step 7 is compared with the authentication tag that was received as an input: if they are identical, then the plaintext is returned; otherwise,FAIL is returned._\n\nThis is seems correctly addressed in the [AES GCM SIV implementation](https://docs.rs/aes-gcm-siv/latest/src/aes_gcm_siv/lib.rs.html#307), where the decrypted buffer is encrypted again before the error is returned - this fix is straightforward to implement in AES GCM. To ensure that these types of cases are covered during testing, it would be valuable to add test cases like [23, 24 ](https://github.com/google/wycheproof/blob/master/testvectors/aes_gcm_test.json#L288)etc from [project wycheproof ](https://github.com/google/wycheproof)to ensure that when a bad tag is used, there is an error on decryption _**and**_ that the plaintext value is not exposed. \n\n### PoC\nTo reproduce this issue, I'm using [test case 23](https://github.com/google/wycheproof/blob/master/testvectors/aes_gcm_test.json#L288) from project wycheproof. \n```rust\n    let key = GenericArray::from_slice(&hex!(\"000102030405060708090a0b0c0d0e0f\"));\n    let nonce = GenericArray::from_slice(&hex!(\"505152535455565758595a5b\"));\n    let tag = GenericArray::from_slice(&hex!(\"d9847dbc326a06e988c77ad3863e6083\")); // bad tag\n    let mut ct = hex!(\"eb156d081ed6b6b55f4612f021d87b39\");\n    let msg = hex!(\"202122232425262728292a2b2c2d2e2f\");\n    let aad = hex!(\"\");\n    let cipher = Aes128Gcm::new(&key);\n    let _plaintext = cipher.decrypt_in_place_detached(&nonce, &aad, &mut ct, &tag);\n    assert_eq!(ct, msg);\n```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "aes-gcm"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.10.0"
      }, {
        "fixed" : "0.10.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.10.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/RustCrypto/AEADs/security/advisories/GHSA-423w-p2w9-r7vq"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-42811"
  }, {
    "type" : "WEB",
    "url" : "https://docs.rs/aes-gcm/latest/src/aes_gcm/lib.rs.html#309"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/RustCrypto/AEADs"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ROBB6TBDAGEQ2WIINR34F3DPSN3FND6K"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RYQCICN6BVC6I75O3F6W4VK4J3MOYDJU"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/U67ZSMNX5V3WTBYPUYF45PSFG4SF5SGF"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2023-0096.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-09-22T16:11:47Z",
    "nvd_published_at" : "2023-09-22T16:15:10Z"
  }
}