CVE-2026-5188

EUVD-2026-21290

10.04.2026, 04:17

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Wrap or Wraparound

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
wolfSSL	CNA	2.3 LOW	NETWORK	HIGH	NONE	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
wolfssl	wolfssl	𝑥 ≤ 5.9.0	CNA

Debian Releases

Debian Product

Codename

wolfssl

bookworm	vulnerable
bullseye	vulnerable
forky	vulnerable
sid	vulnerable
trixie	vulnerable

Ubuntu Releases

Ubuntu Product

Codename

wolfssl

bionic	needs-triage
focal	needs-triage
jammy	needs-triage
noble	needs-triage
questing	needs-triage
xenial	needs-triage

Common Weakness Enumeration

CWE-191 - Integer Underflow (Wrap or Wraparound)
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

References

https://github.com/wolfSSL/wolfssl/pull/10024