CVE-2026-6731

X.509 name constraint bypass via Subject CN treated as a DNS name

6.0 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: High
Availability: None

Exploit likelihood

0.12%Unchanged since Jun 26, 2026

What each source reports

CVE List Score used 6.0

X.509 name constraint bypass via Subject CN treated as a DNS name

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.

Record: CVE-2026-6731
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-295
Updated: 2026-11-02

EUVDEUVD-2026-39555 6.0

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.

Record: EUVD-2026-39555
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-9c3c-227q-3j67 6.0

X.509 name constraint bypass via the Subject Common Name when treated as a DNS-type name. A...

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.

Record: GHSA-9c3c-227q-3j67
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-295
Updated: 2026-11-02

NVD 6.0

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.

Record: CVE-2026-6731
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-295
Updated: 2026-11-02

OSVALPINE-CVE-2026-6731 7.5

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.

Record: ALPINE-CVE-2026-6731
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-03

OSV 6.0

X.509 name constraint bypass via Subject CN treated as a DNS name

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.

Record: CVE-2026-6731
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-295
Updated: 2026-11-02

OSVDEBIAN-CVE-2026-6731 7.5

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.

Record: DEBIAN-CVE-2026-6731
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

OSVJLSEC-2026-755 6.0

X.509 name constraint bypass via the Subject Common Name when treated as a DNS-type name

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.

Record: JLSEC-2026-755
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2026-6731 6.0

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.

Record: UBUNTU-CVE-2026-6731
CVSS 4.0: 6.0 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated: 2026-11-02

Affected products

wolfssl

Affected packages

Affected packages
Package	Affected	Fixed
`wolfssl` Alpine:v3.24	3.9.10 up to 5.9.2-r0	5.9.2-r0
`wolfssl` Debian:12	before 5.5.4-2+deb12u3, plus listed versions 5.5.4-25.5.4-2+deb12u15.5.4-2+deb12u2	5.5.4-2+deb12u3
`wolfssl` Debian:13	before 5.7.2-0.1+deb13u2, plus listed versions 5.7.2-0.15.7.2-0.1+deb13u1	5.7.2-0.1+deb13u2
`wolfSSL_jll` Julia	before 5.9.2+0	5.9.2+0
`wolfssl` Ubuntu:16.04:LTS	All versions, plus listed versions 3.4.8+dfsg-1	None known
`wolfssl` Ubuntu:18.04:LTS	All versions, plus listed versions 3.10.2+dfsg-23.12.0+dfsg-13.12.2+dfsg-13.13.0+dfsg-1	None known
`wolfssl` Ubuntu:20.04:LTS	All versions, plus listed versions 4.1.0+dfsg-24.2.0+dfsg-14.2.0+dfsg-24.2.0+dfsg-34.3.0+dfsg-2	None known
`wolfssl` Ubuntu:22.04:LTS	All versions, plus listed versions 4.6.0-35.0.0-15.1.1-15.2.0-15.2.0-2	None known
`wolfssl` Ubuntu:24.04:LTS	All versions, plus listed versions 5.5.4-25.5.4-2.15.6.4-25.6.6-1.25.6.6-1.35.6.6-1.3build1	None known
`wolfssl` Ubuntu:25.10	All versions, plus listed versions 5.7.2-0.1	None known
`wolfssl` Ubuntu:26.10	All versions, plus listed versions 5.9.1-0.15.9.2-1	None known
`wolfssl` Ubuntu:26.04:LTS	All versions, plus listed versions 5.7.2-0.15.8.2-1.25.8.4-15.9.1-0.1	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	affected, aliases, references	OSV
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-6731 is a medium vulnerability (CVSS 6.0) in Wolfssl, published June 25, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.12%, the 2nd percentile. Fixed in wolfssl 5.9.2-r0.

References

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