CVE-2026-31719 (GCVE-0-2026-31719)
Vulnerability from cvelistv5
Published
2026-05-01 13:56
Modified
2026-08-05 12:24
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
In the Linux kernel, the following vulnerability has been resolved: crypto: krb5enc - fix async decrypt skipping hash verification krb5enc_dispatch_decrypt() sets req->base.complete as the skcipher callback, which is the caller's own completion handler. When the skcipher completes asynchronously, this signals "done" to the caller without executing krb5enc_dispatch_decrypt_hash(), completely bypassing the integrity verification (hash check). Compare with the encrypt path which correctly uses krb5enc_encrypt_done as an intermediate callback to chain into the hash computation on async completion. Fix by adding krb5enc_decrypt_done as an intermediate callback that chains into krb5enc_dispatch_decrypt_hash() upon async skcipher completion, matching the encrypt path's callback pattern. Also fix EBUSY/EINPROGRESS handling throughout: remove krb5enc_request_complete() which incorrectly swallowed EINPROGRESS notifications that must be passed up to callers waiting on backlogged requests, and add missing EBUSY checks in krb5enc_encrypt_ahash_done for the dispatch_encrypt return value. Unset MAY_BACKLOG on the async completion path so the user won't see back-to-back EINPROGRESS notifications.
References
Impacted products
Vendor Product Version
Linux Linux Version: d1775a177f7f38156d541c8a3e3c91eaa6e69699
Version: d1775a177f7f38156d541c8a3e3c91eaa6e69699
Version: d1775a177f7f38156d541c8a3e3c91eaa6e69699
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{
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          "product": "Linux",
          "programFiles": [
            "crypto/krb5enc.c"
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          "vendor": "Linux",
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              "status": "unaffected",
              "version": "0",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: krb5enc - fix async decrypt skipping hash verification\n\nkrb5enc_dispatch_decrypt() sets req-\u003ebase.complete as the skcipher\ncallback, which is the caller\u0027s own completion handler. When the\nskcipher completes asynchronously, this signals \"done\" to the caller\nwithout executing krb5enc_dispatch_decrypt_hash(), completely bypassing\nthe integrity verification (hash check).\n\nCompare with the encrypt path which correctly uses\nkrb5enc_encrypt_done as an intermediate callback to chain into the\nhash computation on async completion.\n\nFix by adding krb5enc_decrypt_done as an intermediate callback that\nchains into krb5enc_dispatch_decrypt_hash() upon async skcipher\ncompletion, matching the encrypt path\u0027s callback pattern.\n\nAlso fix EBUSY/EINPROGRESS handling throughout: remove\nkrb5enc_request_complete() which incorrectly swallowed EINPROGRESS\nnotifications that must be passed up to callers waiting on backlogged\nrequests, and add missing EBUSY checks in krb5enc_encrypt_ahash_done\nfor the dispatch_encrypt return value.\n\n\nUnset MAY_BACKLOG on the async completion path so the user won\u0027t\nsee back-to-back EINPROGRESS notifications."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable AEAD decrypt path is used by Kerberos crypto for network-facing consumers such as RxRPC/AFS and Ceph. A remote peer or network attacker can supply or tamper with encrypted protocol packets that reach `crypto_krb5_decrypt()` and then `krb5enc_decrypt()`.\nAC:L - There is no attacker-uncontrolled race; on a vulnerable deployment using an asynchronous skcipher provider, the bypass follows directly from an async decrypt completion. When uncertain about async-provider deployment details, the higher-severity Low complexity is selected.\nPR:N - The attack can be carried in network traffic toward a kernel network filesystem/protocol endpoint and does not require local privileges on the target. In the strongest plausible scenario, a network attacker tampering with an existing protected flow needs no target-system account.\nUI:N - No victim user action is required once the affected service or client connection is active. Packet processing reaches the vulnerable decrypt path automatically.\nS:U - The impact remains within the kernel/protocol security authority handling the protected traffic. This is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:N - The bug skips integrity verification after decryption but does not by itself disclose plaintext or kernel memory. I found no memory corruption or read primitive associated with the fix.\nI:H - An async decrypt can complete successfully without checking the Kerberos checksum, allowing tampered ciphertext to be accepted as authenticated plaintext. For network storage/filesystem protocols, that can permit forgery or unauthorized modification of protected protocol data.\nA:N - The fixed flaw is an authentication/integrity bypass, and the investigation did not identify a new kernel crash, hang, or resource exhaustion primitive. Bad packets may be rejected or abort protocol state, but that is not a distinct high-availability impact from this bug."
            }
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        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:24:50.735Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/07cbb1bd424370671814a862913c99a6e1441588"
        },
        {
          "url": "https://git.kernel.org/stable/c/e51f42114abbdf47f29dda43e7826be28907fcd2"
        },
        {
          "url": "https://git.kernel.org/stable/c/3bfbf5f0a99c991769ec562721285df7ab69240b"
        }
      ],
      "title": "crypto: krb5enc - fix async decrypt skipping hash verification",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31719",
    "datePublished": "2026-05-01T13:56:13.385Z",
    "dateReserved": "2026-03-09T15:48:24.134Z",
    "dateUpdated": "2026-08-05T12:24:50.735Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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