What is CVE-2026-27145?

CVE-2026-27145 is a medium-severity vulnerability in Go Standard Library Crypto/x509, classified under CWE-407: INEFFICIENT ALGORITHMIC COMPLEXITY. CVSS score: 6.5/10. Published 2026-06-02.

How severe is CVE-2026-27145?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2026-27145 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Go Standard Library Crypto/x509

CVE-2026-27145

(*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…

EPSS: 0.000 (0.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H.

Affected products

Go Standard Library Crypto/x509 — versions 0, 1.26.0-0

Public proof-of-concept exploits

HORKimhab/CVE-2026-27145

References

Frequently asked questions

What is CVE-2026-27145?: CVE-2026-27145 is a medium-severity vulnerability in Go Standard Library Crypto/x509, classified under CWE-407: INEFFICIENT ALGORITHMIC COMPLEXITY. CVSS score: 6.5/10. Published 2026-06-02.
How severe is CVE-2026-27145?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2026-27145 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.