7.5

CVE-2026-6731: X.509 name constraint bypass via Subject CN treated as a DNS name

Analyzed
AliasesUBUNTU-CVE-2026-6731DEBIAN-CVE-2026-6731ALPINE-CVE-2026-6731
Published 25-06-2026Last modified 26-06-2026

Vulnerability summary

CVE-2026-6731 is a high (CVSS 7.5) Improper Certificate Validation vulnerability in wolfssl. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 2.1% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
0.12%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 25-06-2026
    PublishedVulnerability first disclosed.
  2. 26-06-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.12%

Chance of exploitation in the next 30 days

Percentile

2%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.12% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • wolfssl≥ 3.9.10, < 5.9.2-r0
Debian1 product
  • wolfssl< 5.5.4-2+deb12u3 | < 5.7.2-0.1+deb13u2
Ubuntu1 product
  • wolfsslAll versions (No fix recorded)
Wolfssl1 product
  • wolfssl≥ 3.9.10, ≤ 5.9.1 | ≥ 3.9.10, < 5.9.2

4 vendors · 4 products

References

6 links