CVE-2026-27145mediumCWE-606

Inefficient candidate hostname parsing in crypto/x509

33Vexday Risk Score

No sign of exploitation. It has a public proof of concept.

ssvc Attendcvss 6.5epss 0.6%

from disclosure to weapon1 days

Published on NVDJun 2

1st PoC+1d

exploitation probability

0.6%top 54% of all CVEs

observed exploitation

nono source reports it

1 public exploit(s)

(*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: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

public PoCs found — 1

githubgithub.com/HORKimhab/CVE-2026-27145★ 0

⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.

References