{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63567", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "state": "PUBLISHED", "assignerShortName": "bcorg", "dateReserved": "2026-07-16T23:48:46.076Z", "datePublished": "2026-10-02T06:58:32.487Z", "dateUpdated": "2026-10-02T06:58:32.487Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-10-02T06:58:32.487Z"}, "title": "IesEngine block-cipher mode checks padding before MAC (CBC padding oracle)", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-203", "description": "CWE-203 Observable Discrepancy", "type": "CWE"}]}], "impacts": [{"descriptions": [{"lang": "en", "value": "Confidentiality: recovery of IES/ECIES plaintext via a chosen-ciphertext padding 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/engines/IesEngine.cs"], "versions": [{"status": "affected", "version": "0", "lessThan": "2.7.0", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under the same key pair, to recover its plaintext via a CBC padding-oracle attack, because in block-cipher mode the engine decrypts the ciphertext and removes its padding before verifying the MAC. A padding failure is therefore reported with a different error message, and without the MAC computation, compared with a MAC failure. Only applications that construct IesEngine directly with a padded block cipher, such as AES in CBC mode with PKCS#7 padding, are affected; stream-mode IES is not.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under the same key pair, to recover its plaintext via a CBC padding-oracle attack, because in block-cipher mode the engine decrypts the ciphertext and removes its padding before verifying the MAC. A padding failure is therefore reported with a different error message, and without the MAC computation, compared with a MAC failure. Only applications that construct IesEngine directly with a padded block cipher, such as AES in CBC mode with PKCS#7 padding, are affected; stream-mode IES is not."}]}], "references": [{"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63567", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d", "tags": ["patch"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/eaa42e1e8125b3e2e25e365c4194c7cd5932360b", "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-J7SXX2NS", "ANT-2026-SNRMZ9MS"]}}}

{}

{"affected": [{"affectedData": [{"collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography", "defaultStatus": "unaffected", "packageName": "BouncyCastle.Cryptography", "product": "bc-csharp", "programFiles": ["crypto/src/crypto/engines/IesEngine.cs"], "repo": "https://github.com/bcgit/bc-csharp", "vendor": "Legion of the Bouncy Castle Inc.", "versions": [{"lessThan": "2.7.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under the same key pair, to recover its plaintext via a CBC padding-oracle attack, because in block-cipher mode the engine decrypts the ciphertext and removes its padding before verifying the MAC. A padding failure is therefore reported with a different error message, and without the MAC computation, compared with a MAC failure. Only applications that construct IesEngine directly with a padded block cipher, such as AES in CBC mode with PKCS#7 padding, are affected; stream-mode IES is not."}], "id": "CVE-2026-63567", "lastModified": "2026-10-02T14:44:52.247", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.2, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}]}, "published": "2026-10-02T07:16:37.127", "references": [{"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "url": "https://github.com/bcgit/bc-csharp/commit/eaa42e1e8125b3e2e25e365c4194c7cd5932360b"}, {"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "url": "https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d"}, {"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63567"}], "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-203"}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}]}

{}

{"created": "2026-10-02T09:15:08.529371+00:00", "updated": "2026-10-02T09:15:08.529376+00:00", "vendors": []}