9.1

CVE-2026-89134: Subject CN name-constraint check bypassed when non-DNS SAN present

Analyzed
AliasesUBUNTU-CVE-2026-89134DEBIAN-CVE-2026-89134ALPINE-CVE-2026-89134
Published 27-09-2026Last modified 29-09-2026

Vulnerability summary

CVE-2026-89134 is a critical (CVSS 9.1) Improper Certificate Validation vulnerability in wolfssl. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 6.7% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
9.1/10
010
Critical · v3.1 (NVD)
EPSS score
0.17%
0%100%
Low · +0.02 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 27-09-2026
    PublishedVulnerability first disclosed.
  2. 29-09-2026
    Last modifiedVulnerability information updated.

Description

A certificate with no dNSName SAN but another SAN type present (e.g. registeredID or iPAddress) bypassed the Subject CN dNSName name-constraint check. The CN-as-DNS fallback was gated on cert->subjectCN != NULL && cert->altNames == NULL && !cert->isCA instead of "no dNSName SAN", so an out-of-scope CN was accepted. This incomplete fix from CVE-2026-6731, leading to the name-constraint check issue, was introduced in wolfSSL version 5.9.2.

CVSS metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.17%

Chance of exploitation in the next 30 days

Percentile

7%

Versus all other CVEs

30-day change

Increase +0.02 pp

From 0.16% 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, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • wolfssl< 5.9.4-r0
Debian1 product
  • wolfsslAll versions (No fix recorded)
Ubuntu1 product
  • wolfsslAll versions (No fix recorded)
Wolfssl1 product

4 vendors · 4 products

References

5 links