6.5

CVE-2026-27145: Inefficient candidate hostname parsing in crypto/x509

Awaiting analysis
AliasesRHSA-2026:46394RHSA-2026:53416UBUNTU-CVE-2026-27145
Published 02-06-2026Last modified 18-09-2026

Vulnerability summary

CVE-2026-27145 is a medium (CVSS 6.5) Unchecked Input for Loop Condition vulnerability in go standard library crypto/x509. EPSS estimates a 0.59% chance of exploitation in the next 30 days, higher than 48.2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6.5, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.59%
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

Advisory lineage

Upstream 0 · Downstream 61 · Related 61
MGASA-2026-0276OPENSUSE-SU-2026:10959-1OPENSUSE-SU-2026:10960-1OPENSUSE-SU-2026:10975-1OPENSUSE-SU-2026:20976-1OPENSUSE-SU-2026:20977-1

Timeline

  1. 02-06-2026
    PublishedVulnerability first disclosed.
  2. 18-09-2026
    Last modifiedVulnerability information updated.

Description

(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.59%

Chance of exploitation in the next 30 days

Percentile

48%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.59% 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.

Chainguard200 products
  • aactl< 0.4.12-r54
  • act< 0.2.89-r1
  • actionlintAll versions (No fix recorded)
  • actions-runner-controller< 0.14.2-r2
  • addon-resizer< 1.8.23-r20

1 vendor · 200 products · Showing 200 of 2748

References

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