{"id":"CVE-2026-69247","summary":"cryptography: PKCS#7 EnvelopedData decryption exposes a Bleichenbacher oracle through distinguishable errors and timing","details":"cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. From 44.0.0 until 50.0.0, pkcs7_decrypt_der, pkcs7_decrypt_pem, and pkcs7_decrypt_smime reported the outcome of decrypting a RecipientInfo's encryptedKey in several distinguishable ways, one of which disclosed the exact length recovered from the RSA operation. The same distinction was also observable by timing. An application that decrypts attacker-supplied EnvelopedData and reflects the outcome gives the attacker a Bleichenbacher oracle against the content-encryption key. Decryption ran as RSA PKCS#1 v1.5 decrypt of encryptedKey, build an AES cipher from the result, then AES-CBC decrypt and PKCS#7 unpad. Invalid RSA padding, a valid padding with a bad key length, a correct length with a wrong key, and the real key each failed or succeeded differently. Case 1 is reachable only where the linked library lacks implicit rejection: OpenSSL 3.0 and 3.1, LibreSSL, and BoringSSL. Exploitation requires a service that auto-decrypts untrusted EnvelopedData matching the victim certificate and answers adaptively at high volume, such as an S/MIME gateway or mail filter. This issue is fixed in 50.0.0.","aliases":["GHSA-g6cj-pr64-35w5","PYSEC-2026-3552"],"modified":"2026-08-06T11:46:03.213182120Z","published":"2026-08-03T21:16:32.047Z","related":["CGA-g67v-j9r6-8vjv"],"database_specific":{"cwe_ids":["CWE-208","CWE-209"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69247.json","cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69247.json"},{"type":"ADVISORY","url":"https://github.com/pyca/cryptography/security/advisories/GHSA-g6cj-pr64-35w5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-69247"},{"type":"FIX","url":"https://github.com/pyca/cryptography/commit/53fccd93413a8d7f07d6d8999681f27b75cffa3f"},{"type":"FIX","url":"https://github.com/pyca/cryptography/pull/15369"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pyca/cryptography","events":[{"introduced":"f299a48153650f2dd87716343f2daa7cd39a1f59"},{"fixed":"53fccd93413a8d7f07d6d8999681f27b75cffa3f"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"44.0.0"},{"fixed":"50.0.0"}]}}],"versions":["49.0.0","48.0.0","47.0.0","46.0.1","46.0.0","45.0.0","44.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-69247.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"}]}