{"api_version":"1","generated_at":"2026-06-03T11:06:23+00:00","cve":"CVE-2026-27145","urls":{"html":"https://cve.report/CVE-2026-27145","api":"https://cve.report/api/cve/CVE-2026-27145.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-27145","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-27145"},"summary":{"title":"Inefficient candidate hostname parsing in crypto/x509","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.","state":"PUBLISHED","assigner":"Go","published_at":"2026-06-02 23:16:35","updated_at":"2026-06-02 23:16:35"},"problem_types":["CWE-407: Inefficient Algorithmic Complexity"],"metrics":[],"references":[{"url":"https://go.dev/cl/783621","name":"https://go.dev/cl/783621","refsource":"security@golang.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://pkg.go.dev/vuln/GO-2026-5037","name":"https://pkg.go.dev/vuln/GO-2026-5037","refsource":"security@golang.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://go.dev/issue/79694","name":"https://go.dev/issue/79694","refsource":"security@golang.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw","name":"https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw","refsource":"security@golang.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-27145","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27145","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Go standard library","product":"crypto/x509","version":"affected 1.25.11 semver","platforms":[]},{"source":"CNA","vendor":"Go standard library","product":"crypto/x509","version":"affected 1.26.0-0 1.26.4 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Jakub Ciolek - https://ciolek.dev/","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://pkg.go.dev","defaultStatus":"unaffected","packageName":"crypto/x509","product":"crypto/x509","programRoutines":[{"name":"HostnameError.Error"},{"name":"matchHostnames"},{"name":"Certificate.Verify"},{"name":"Certificate.VerifyHostname"}],"vendor":"Go standard library","versions":[{"lessThan":"1.25.11","status":"affected","version":"0","versionType":"semver"},{"lessThan":"1.26.4","status":"affected","version":"1.26.0-0","versionType":"semver"}]}],"credits":[{"lang":"en","value":"Jakub Ciolek - https://ciolek.dev/"}],"descriptions":[{"lang":"en","value":"(*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."}],"problemTypes":[{"descriptions":[{"description":"CWE-407: Inefficient Algorithmic Complexity","lang":"en"}]}],"providerMetadata":{"dateUpdated":"2026-06-02T22:01:36.954Z","orgId":"1bb62c36-49e3-4200-9d77-64a1400537cc","shortName":"Go"},"references":[{"url":"https://go.dev/cl/783621"},{"url":"https://go.dev/issue/79694"},{"url":"https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw"},{"url":"https://pkg.go.dev/vuln/GO-2026-5037"}],"title":"Inefficient candidate hostname parsing in crypto/x509"}},"cveMetadata":{"assignerOrgId":"1bb62c36-49e3-4200-9d77-64a1400537cc","assignerShortName":"Go","cveId":"CVE-2026-27145","datePublished":"2026-06-02T22:01:36.954Z","dateReserved":"2026-02-17T19:57:28.435Z","dateUpdated":"2026-06-02T22:01:36.954Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-06-02 23:16:35","lastModifiedDate":"2026-06-02 23:16:35","problem_types":["CWE-407: Inefficient Algorithmic Complexity"],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"27145","Ordinal":"1","Title":"Inefficient candidate hostname parsing in crypto/x509","CVE":"CVE-2026-27145","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"27145","Ordinal":"1","NoteData":"(*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.","Type":"Description","Title":"Inefficient candidate hostname parsing in crypto/x509"}]}}}