CVE-2026-15999

Full vulnerability record from the local CVENow database.

Description

Improper validation of integrity check value in the AES-CCM implementation (CcmParameters and CcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to modify CCM-encrypted content without detection via an AlgorithmIdentifier whose CCMParameters declare an authentication tag (aes-ICVlen) of zero or another length outside the RFC 5084 set, because CcmParameters accepted any value and CcmBlockCipher validated the tag length only when encrypting, so decryption compared a zero-length or very short tag. Affected paths include ParameterUtilities.GetCipherParameters, used by CmsEnvelopedData and CmsEnvelopedDataParser for EnvelopedData encrypted with AES-CCM, and any caller passing an unchecked tag length to CcmBlockCipher for decryption.

Severity

HIGH

CVSS score

8.2 (v4.0)

Vulnerability status

Analyzed

Source identifier

91579145-5d7b-4cc5-b925-a0262ff19630

Published

2026-10-02 07:16:36.193000

Last modified

2026-10-27 16:34:53.500000

View original CVE JSON

{
  "id": "CVE-2026-15999",
  "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630",
  "published": "2026-10-02T07:16:36.193",
  "lastModified": "2026-10-27T16:34:53.500",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
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      "lang": "en",
      "value": "Improper validation of integrity check value in the AES-CCM implementation (CcmParameters and CcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to modify CCM-encrypted content without detection via an AlgorithmIdentifier whose CCMParameters declare an authentication tag (aes-ICVlen) of zero or another length outside the RFC 5084 set, because CcmParameters accepted any value and CcmBlockCipher validated the tag length only when encrypting, so decryption compared a zero-length or very short tag. Affected paths include ParameterUtilities.GetCipherParameters, used by CmsEnvelopedData and CmsEnvelopedDataParser for EnvelopedData encrypted with AES-CCM, and any caller passing an unchecked tag length to CcmBlockCipher for decryption."
    }
  ],
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      "affectedData": [
        {
          "vendor": "Legion of the Bouncy Castle Inc.",
          "product": "bc-csharp",
          "defaultStatus": "unaffected",
          "collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography",
          "packageName": "BouncyCastle.Cryptography",
          "programFiles": [
            "crypto/src/asn1/cms/CcmParameters.cs",
            "crypto/src/crypto/modes/CcmBlockCipher.cs"
          ],
          "repo": "https://github.com/bcgit/bc-csharp",
          "versions": [
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              "version": "0",
              "lessThan": "2.7.0",
              "versionType": "semver",
              "status": "affected"
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          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "valueDensity": "NOT_DEFINED",
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    "cvssMetricV31": [
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          "scope": "UNCHANGED",
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    "ssvcV203": [
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      "url": "https://github.com/bcgit/bc-csharp/commit/2818bdfa55efd58b0d6a1c75f360b8404d879780",
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