{"id":"UBUNTU-CVE-2026-69247","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.","modified":"2026-09-17T19:57:34.741141631Z","published":"2026-08-03T22:16:00Z","related":["USN-8776-1"],"upstream":["CVE-2026-69247"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-69247"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-69247"},{"type":"REPORT","url":"https://github.com/pyca/cryptography/security/advisories/GHSA-g6cj-pr64-35w5"},{"type":"REPORT","url":"https://github.com/pyca/cryptography/pull/15369"},{"type":"REPORT","url":"https://github.com/pyca/cryptography/commit/53fccd93413a8d7f07d6d8999681f27b75cffa3f"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8776-1"}],"affected":[{"package":{"name":"python-cryptography","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-cryptography?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"46.0.5-1ubuntu2.2"}]}],"versions":["43.0.0-1ubuntu1","46.0.1-1ubuntu2","46.0.5-1ubuntu1","46.0.5-1ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-cryptography","binary_version":"46.0.5-1ubuntu2.2"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-69247.json"}}],"schema_version":"1.9.0","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"},{"type":"Ubuntu","score":"medium"}]}