Vulnerability · Published Jun 25, 2026 · Assigned by wolfSSL
CVE-2026-6731X.509 name constraint bypass via Subject CN treated as a DNS name
Medium 6.0
In plain English
A medium-severity improper certificate validation in wolfSSL from wolfSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)6.0Medium
Exploit odds (30 days)0.1%top 97.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
X.509 name constraint bypass via the Subject Common Name when treated as a DNS-type name. A certificate whose Subject CN violates an issuing CA's DNS name constraints could be accepted.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | wolfssl | 5.9.2-r0 | ALPINE-CVE-2026-6731 |
| Debian:12 | wolfssl | 5.5.4-2+deb12u3 | DEBIAN-CVE-2026-6731 |
| Debian:13 | wolfssl | 5.7.2-0.1+deb13u2 | DEBIAN-CVE-2026-6731 |
| Ubuntu:22.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-6731 |
| Ubuntu:24.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-6731 |
| Ubuntu:25.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-6731 |
| Ubuntu:26.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-6731 |
| Ubuntu:26.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-6731 |
Affected products (as reported)
Weakness: CWE-295 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N