{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-103601", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "state": "PUBLISHED", "assignerShortName": "bcorg", "dateReserved": "2026-09-30T23:01:10.053Z", "datePublished": "2026-10-02T07:09:17.064Z", "dateUpdated": "2026-10-02T07:09:17.064Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-10-02T07:09:17.064Z"}, "title": "CcmBlockCipher and KCcmBlockCipher leave unverified plaintext in the output buffer after a failed tag check", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-354", "description": "CWE-354 Improper Validation of Integrity Check Value", "type": "CWE"}]}], "impacts": [{"descriptions": [{"lang": "en", "value": "Confidentiality (unverified plaintext left in the caller's buffer after a failed tag check, giving a CTR decryption oracle)"}]}], "affected": [{"vendor": "Legion of the Bouncy Castle Inc.", "product": "bc-csharp", "collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography", "packageName": "BouncyCastle.Cryptography", "repo": "https://github.com/bcgit/bc-csharp", "programFiles": ["crypto/src/crypto/modes/CcmBlockCipher.cs", "crypto/src/crypto/modes/KCcmBlockCipher.cs"], "versions": [{"status": "affected", "version": "0", "lessThan": "2.7.0", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "Release of unverified plaintext in the CCM (CcmBlockCipher) and DSTU 7624 CCM (KCcmBlockCipher) AEAD modes in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to obtain decryptions of ciphertexts of their choosing via forged messages sent to an application that lets the output buffer of a failed decryption be observed, for example through buffer reuse or logging, because decryption wrote the recovered plaintext into the caller-supplied output buffer before checking the authentication tag and left it there when the check failed. Only decryption into a caller-supplied buffer is affected; methods that return a newly allocated array are not.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Release of unverified plaintext in the CCM (CcmBlockCipher) and DSTU 7624 CCM (KCcmBlockCipher) AEAD modes in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to obtain decryptions of ciphertexts of their choosing via forged messages sent to an application that lets the output buffer of a failed decryption be observed, for example through buffer reuse or logging, because decryption wrote the recovered plaintext into the caller-supplied output buffer before checking the authentication tag and left it there when the check failed. Only decryption into a caller-supplied buffer is affected; methods that return a newly allocated array are not."}]}], "references": [{"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103601", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/e0868323645a063cb2479646e93c1449dc338de5", "tags": ["patch"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/4ddb1d0bfeae3a81b18f4446d8cc8a7871bd2d9f", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 8.2, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.", "type": "finder"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "Claude Opus 5.5"}, "x_antReportIds": ["ANT-2026-A41MAVE2"]}}}

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