Vulnerability Description
Bleichenbacher padding oracle in PKCS#7 KTRI decryption. When decrypting PKCS#7 EnvelopedData using RSA PKCS#1 v1.5 key transport, wolfSSL returned distinguishable error codes depending on whether RSA padding validation failed versus whether the decrypted content was malformed. An attacker able to submit crafted EnvelopedData messages and observe error responses could use this as a padding oracle to incrementally recover the encrypted Content Encryption Key (CEK). The fix generates a deterministic pseudo-random fake CEK on padding failure (via HMAC-SHA256) and proceeds with decryption identically, using constant-time operations throughout, so that all failure paths produce the same error regardless of padding validity.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Wolfssl | Wolfssl | >= 3.9.10, < 5.9.2 |
Related Weaknesses (CWE)
References
- https://github.com/wolfSSL/wolfssl/pull/10203Issue Tracking
- https://www.wolfssl.com/docs/security-vulnerabilities/Vendor Advisory
FAQ
What is CVE-2026-6291?
CVE-2026-6291 is a vulnerability with a CVSS score of 6.5 (MEDIUM). Bleichenbacher padding oracle in PKCS#7 KTRI decryption. When decrypting PKCS#7 EnvelopedData using RSA PKCS#1 v1.5 key transport, wolfSSL returned distinguishable error codes depending on whether RSA...
How severe is CVE-2026-6291?
CVE-2026-6291 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-6291?
Check the references section above for vendor advisories and patch information. Affected products include: Wolfssl Wolfssl.