CVE-2026-33810

package main import ( "crypto/x509" "crypto/x509/pkix" "encoding/pem" "fmt" "strings" ) // This is a conceptual PoC to demonstrate the validation logic issue. // Actual exploitation requires generating specific certificate chains. func main() { // Simulate a Name Constraint with Excluded Subtree constraint := pkix.NameConstraints{ ExcludedDNSDomains: []string{"excluded.com"}, } // Simulate a Wildcard SAN in the certificate (different case) certSAN := "*.Excluded.Com" // Note the capital E and C // The vulnerability implies that the verification logic fails here // because it does not normalize case before checking constraints. matched := false for _, domain := range constraint.ExcludedDNSDomains { // Vulnerable logic comparison (pseudo-code of the bug) if strings.Contains(certSAN, domain) { matched = true break } } if !matched { fmt.Println("[VULNERABLE] Certificate passed validation despite violating exclusion constraint.") } else { fmt.Println("[SAFE] Certificate correctly rejected.") } }

{"cve": {"id": "CVE-2026-33810", "sourceIdentifier": "[email protected]", "published": "2026-04-08T02:16:03.950", "lastModified": "2026-04-20T18:16:26.813", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "When verifying a certificate chain containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs which use a different case than the constraint. This only affects validation of otherwise trusted certificate chains, issued by a root CA in the VerifyOptions.Roots CertPool, or in the system certificate pool."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N", "baseScore": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 4.2}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-295"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.26.0", "versionEndExcluding": "1.26.2", "matchCriteriaId": "39FE9BAF-55E9-43AA-B14E-239E7EF1D65D"}]}]}], "references": [{"url": "https://go.dev/cl/763763", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://go.dev/issue/78332", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU", "source": "[email protected]", "tags": ["Mailing List", "Release Notes"]}, {"url": "https://pkg.go.dev/vuln/GO-2026-4866", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/04/19/4", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "http://www.openwall.com/lists/oss-security/2026/04/20/1", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}