Is CVE-2026-6291 in the CISA KEV catalog?

No. CVE-2026-6291 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-6291?

CVE-2026-6291 has a CVSS v3 base score of 6.5 (Moderate).

What is the EPSS score for CVE-2026-6291?

CVE-2026-6291 has an EPSS score of 0.15% (5th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-6291?

Upgrade wolfssl to 5.9.2 or later.

CVE & CISA-KEV Catalog

CVE-2026-6291

MEDIUM

6.5

CVSS v3

NVD

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.

CWE-208

How to fix

Remediation Available

wolfsslNVD

Affected:>= 3.9.10, < 5.9.2Fixed in:5.9.2CVE-2026-6291derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityNone

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Exploit Intelligence

0.15%probability of exploitation in 30 days

5thpercentile

Low risk: more likely to be exploited than 5% of all known CVEs.

References

Vendor Advisory1

wolfssl.com

Issue Tracking1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-26.