CVE-2026-6291
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).
Does this matter?
Lower severity and a low EPSS score (0.24%). Track it; it rarely justifies an emergency change on its own.
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 4.0
- 6.0 MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.24% probability · 16th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-208
- Affected
- wolfssl/wolfssl
- Source
- facts@wolfssl.com
References
- https://github.com/wolfSSL/wolfssl/pull/10203Issue Tracking
- https://www.wolfssl.com/docs/security-vulnerabilities/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.