{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-110310", "assignerOrgId": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "state": "PUBLISHED", "assignerShortName": "AMZN", "dateReserved": "2026-10-13T20:08:06.762Z", "datePublished": "2026-10-14T19:37:48.420Z", "dateUpdated": "2026-10-14T19:46:28.634Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "shortName": "AMZN", "dateUpdated": "2026-10-14T19:46:28.634Z" }, "title": "RSA PKCS#1 v1.5 padding oracle via legacy envelope key format downgrade in Amazon S3 Encryption Client for .NET", "problemTypes": [ { "descriptions": [ { "lang": "en", "cweId": "CWE-204", "description": "CWE-204 Observable response discrepancy", "type": "CWE" } ] }, { "descriptions": [ { "lang": "en", "cweId": "CWE-757", "description": "CWE-757 Selection of Less-Secure algorithm during negotiation ('algorithm downgrade')", "type": "CWE" } ] } ], "impacts": [ { "capecId": "CAPEC-463", "descriptions": [ { "lang": "en", "value": "CAPEC-463 Padding Oracle Crypto Attack" } ] } ], "affected": [ { "vendor": "Amazon", "product": "Amazon.Extensions.S3.Encryption", "versions": [ { "status": "affected", "version": "2.1.0", "lessThanOrEqual": "2.*", "versionType": "custom" }, { "status": "affected", "version": "3.0.0", "lessThanOrEqual": "3.2.1", "versionType": "custom" }, { "status": "affected", "version": "4.0.0", "lessThanOrEqual": "4.0.2", "versionType": "custom" } ], "defaultStatus": "unaffected" } ], "cpeApplicability": [ { "operator": "OR", "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:a:amazon:amazon.extensions.s3.encryption:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.1.0", "versionEndIncluding": "2.*" }, { "vulnerable": true, "criteria": "cpe:2.3:a:amazon:amazon.extensions.s3.encryption:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.0", "versionEndIncluding": "3.2.1" }, { "vulnerable": true, "criteria": "cpe:2.3:a:amazon:amazon.extensions.s3.encryption:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0.0", "versionEndIncluding": "4.0.2" } ] } ] } ], "descriptions": [ { "lang": "en", "value": "A remote user who can read encrypted objects in the S3 bucket can force a padding downgrade by altering the padding scheme recorded in an object's metadata to legacy PKCS#1 v1.5. Since this padding scheme is susceptible to the well-known Bleichenbacher attack, the user can use a PKCS#1 v1.5 padding oracle to recover the RSA-wrapped envelope key and decrypt the object.\n\n\n\nTo remediate this issue, we recommend that users upgrade to version 3.2.2 or 4.0.3. The 1.x and 2.x lines will not be patched, users of those lines need to migrate to 3.2.2 or 4.0.3.", "supportingMedia": [ { "type": "text/html", "base64": false, "value": "

A remote user who can read encrypted objects in the S3 bucket can force a padding downgrade by altering the padding scheme recorded in an object's metadata to legacy PKCS#1 v1.5. Since this padding scheme is susceptible to the well-known Bleichenbacher attack, the user can use a PKCS#1 v1.5 padding oracle to recover the RSA-wrapped envelope key and decrypt the object.

To remediate this issue, we recommend that users upgrade to version 3.2.2 or 4.0.3. The 1.x and 2.x lines will not be patched, users of those lines need to migrate to 3.2.2 or 4.0.3.

" } ] } ], "references": [ { "url": "https://www.nuget.org/packages/Amazon.Extensions.S3.Encryption/3.2.2", "tags": [ "release-notes", "patch" ] }, { "url": "https://www.nuget.org/packages/Amazon.Extensions.S3.Encryption/4.0.3", "tags": [ "release-notes", "patch" ] }, { "url": "https://aws.amazon.com/security/security-bulletins/2026-135-aws/", "tags": [ "vendor-advisory" ] }, { "url": "https://github.com/aws/amazon-s3-encryption-client-dotnet/security/advisories/GHSA-322w-f6rw-r4fj", "tags": [ "third-party-advisory" ] } ], "metrics": [ { "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ], "cvssV3_1": { "version": "3.1", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE", "baseSeverity": "MEDIUM", "baseScore": 5.3, "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N" } }, { "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ], "cvssV4_0": { "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "LOW", "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": "MEDIUM", "baseScore": 6, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N" } } ], "source": { "discovery": "UNKNOWN" }, "x_generator": { "engine": "Vulnogram 1.0.5" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-10-14T19:46:05.003309Z", "id": "CVE-2026-110310", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-14T19:46:15.647Z" } } ] } }