CVE-2026-271456.5MediumCWE-407

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

Go standard library · crypto/x509

Vendor fix available · Affected: Go standard library crypto/x509 · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.6%probability of exploitation in the next 30 days

48th percentile

050100

Higher than 48% of scored CVEs

6.5MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

(*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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

Go standard library · crypto/x509before 1.25.11; from 1.26.0-0 before 1.26.4

On the Atlas

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Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Inefficient Algorithmic Complexity · Denial of Service
Vendor: Go standard library
Published: June 2026
Band: Unlikely (under 1%), June 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-27145 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.

References

28 more references are in the CVE record.