{"cve":"CVE-2026-27145","nvd":{"published":"2026-06-02T23:16:35.570","modified":"2026-09-18T13:17:43.283","status":"Awaiting Analysis","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H","score":6.5},"cwes":["CWE-606"],"references":["https://go.dev/cl/783621","https://go.dev/issue/79694","https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw","https://pkg.go.dev/vuln/GO-2026-5037","https://access.redhat.com/errata/RHSA-2026:23262"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:37:48.043517290+00:00"},"epss":{"cve":"CVE-2026-27145","score":0.00591,"percentile":0.48263,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GO-2026-5037","url":"https://osv.dev/vulnerability/GO-2026-5037","summary":"Inefficient candidate hostname parsing in crypto/x509","modified":"2026-10-02T10:41:43.926190093Z","packages":[{"ecosystem":"Go","name":"stdlib","purl":"pkg:golang/stdlib","ranges":["<1.25.11",">=1.26.0-0 <1.26.4"],"fixed":["1.25.11","1.26.4"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}