{"vulnerability": "GHSA-g6cj-pr64-35w5", "sightings": [{"uuid": "8f5d1831-0f15-4e25-b7da-978e974f7fdd", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "GHSA-g6cj-pr64-35w5", "type": "seen", "source": "https://gist.github.com/alon710/aae79fe7bcf7e7234c2912679ec8c451", "content": "# CVE-2026-69247: CVE-2026-69247: Bleichenbacher Oracle in pyca/cryptography PKCS#7 Decryption\n\n> **CVSS Score:** 8.2\n> **Published:** 2026-08-03\n> **Full Report:** https://cvereports.com/reports/CVE-2026-69247\n\n## Summary\nA side-channel vulnerability in pyca/cryptography (versions 44.0.0 through 49.9.9) allows unauthenticated remote attackers to expose a Bleichenbacher oracle. This flaw exists within the PKCS#7 decryption module (specifically pkcs7_decrypt_der, pkcs7_decrypt_pem, and pkcs7_decrypt_smime) during Content Encryption Key (CEK) decryption when using RSA PKCS#1 v1.5 padding. Differences in error classification and symmetric execution timing allow an attacker to reconstruct plaintext keys.\n\n## TL;DR\nA Bleichenbacher side-channel timing and error oracle in pyca/cryptography before version 50.0.0 allows unauthenticated remote attackers to recover Content Encryption Keys (CEK) and decrypt sensitive S/MIME messages by submitting crafted PKCS#7 ciphertexts and observing decryption responses.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-208: Observable Timing Discrepancy\n- **Attack Vector**: Network (AV:N)\n- **CVSS v4.0 Score**: 8.2 (High)\n- **Exploit Status**: Proof of concept code exists in library test suites; no public weaponized exploits.\n- **CISA KEV Status**: Not listed\n- **Mitigation Standard**: RFC 3218 (Key substitution on failure)\n- **Affected Functionality**: pkcs7_decrypt_der, pkcs7_decrypt_pem, pkcs7_decrypt_smime\n\n## Affected Systems\n\n- pyca/cryptography Python libraries (versions 44.0.0 through 49.9.9)\n- S/MIME processing gateways relying on affected cryptography versions\n- Email processing filters and document ingestion pipelines handling PKCS#7 EnvelopedData\n- **cryptography**: >= 44.0.0, < 50.0.0 (Fixed in: `50.0.0`)\n\n## Mitigation\n\n- Upgrade the pyca/cryptography package to version 50.0.0 or higher.\n- Design S/MIME and mail-processing applications to handle decryption asynchronously in background queues with uniform execution times.\n- Sanitize application error messages to ensure that decryption failures always return a generic error code without leaking padding or size metrics.\n- Implement strict rate-limiting on endpoints that accept and decrypt encrypted PKCS#7 payloads.\n\n**Remediation Steps:**\n1. Identify all Python execution environments and containerized applications utilizing the pyca/cryptography library.\n2. Execute `pip install --upgrade cryptography>=50.0.0` in your deployment pipelines and update requirements.txt/poetry.lock files.\n3. Re-build and redeploy application containers to integrate the updated binary wheel.\n4. Review application-level error handlers to verify that ValueError exceptions from pkcs7_decrypt functions are caught and mapped to unified, safe error responses.\n\n## References\n\n- [GitHub Security Advisory GHSA-g6cj-pr64-35w5](https://github.com/pyca/cryptography/security/advisories/GHSA-g6cj-pr64-35w5)\n- [Fix Commit 53fccd93](https://github.com/pyca/cryptography/commit/53fccd93413a8d7f07d6d8999681f27b75cffa3f)\n- [GitHub Pull Request 15369](https://github.com/pyca/cryptography/pull/15369)\n- [CVE-2026-69247 Record on CVE.org](https://www.cve.org/CVERecord?id=CVE-2026-69247)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-69247) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-08-04T00:32:44.722747Z"}]}