CVE-2026-27138 | Panic in name constraint checking for malformed certificates in crypto/x509

Certificate verification can panic when a certificate in the chain has an empty DNS name and another certificate in the chain has excluded name constraints. This can crash programs that are either directly verifying X.509 certificate chains, or those that use TLS.

Published: 2026-03-06 Last update: 2026-04-21 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27138 is rated Low Risk (25.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-27138

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-07 — 0.02% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27138

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-27138

GitHub Security Advisory for CVE-2026-27138

GHSA-ph5j-38mg-j6hp · Severity: medium — Certificate verification can panic when a certificate in the chain has an empty DNS name and...

OS Trackers for CVE-2026-27138

vendor priority summary link
alpine — CVE-2026-27138: 1 source package rows (go); 2 state rows across 1 repos (edge-community); fixed 2, open 0. https://security.alpinelinux.org/vuln/CVE-2026-27138
debian unimportant CVE-2026-27138 unimportant priority: Debian including 5 source packages (golang-1.15, golang-1.19, golang-1.24, golang-1.25, golang-1.26), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 7. https://security-tracker.debian.org/tracker/CVE-2026-27138
redhat low — https://access.redhat.com/security/cve/CVE-2026-27138
suse high — https://www.suse.com/security/cve/CVE-2026-27138/
ubuntu medium CVE-2026-27138 medium priority: Ubuntu including 3 source packages (golang-1.24, golang-1.25, golang-1.26), 12 status rows across 4 suites (jammy, noble, questing, upstream): DNE 5, needs-triage 4, not-affected 2, released 1. https://ubuntu.com/security/CVE-2026-27138

Affected software / configurations for CVE-2026-27138

Vendor Product Version Raw CPE
golang go 1.26.0 cpe:2.3:a:golang:go:1.26.0:*:*:*:*:*:*:*

References for CVE-2026-27138

cvelogic Threat Intelligence