CVE-2026-4821

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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.", "supportingMedia": [{"type": "text/html", "value": "An improper neutralization of special elements vulnerability was identified in GitHub Enterprise Server that allowed an authenticated Management Console administrator&nbsp;to execute arbitrary OS commands&nbsp;via&nbsp;shell metacharacter injection in proxy configuration fields such as&nbsp;<code>http_proxy.&nbsp;</code>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. 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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.20.0,3.20.1)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.19.0,3.19.4]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.18.0,3.18.7]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.17.0,3.17.13]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.16.0,3.16.16]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.15.0,3.15.20]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.14.0,3.14.25]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Enterprise Server", "source": "cna", "vendor": "GitHub"}, "product": "enterprise_server", "vendor": "github"}], "analysis": {"en": {"generated_at": "2026-04-22T06:19:03.086928+00:00", "value": {"mitigation_remediation": ["Apply the latest patch by upgrading to GitHub Enterprise Server 3.20.1 or newer, ensuring all earlier vulnerable releases are removed.", "Validate proxy configuration values to accept only well\u2011formed URLs and reject any shell metacharacters.", "Restrict Management Console administrator privileges to a minimal trusted group and regularly monitor for unauthorized configuration changes."], "summary": {"action": "Immediate Patch", "impact": "Remote Code Execution"}, "threat_synthesis": {"affected_systems": "GitHub Enterprise Server versions prior to 3.21 are affected. The issue was addressed in releases 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21 and 3.14.26, and the vulnerability is present in all earlier releases.", "description_and_impact": "An improper neutralization of special elements vulnerability allows an authenticated Management Console administrator to inject shell metacharacters into proxy configuration fields, such as the http_proxy setting, and execute arbitrary operating\u2011system commands. This results in full control of the server, compromising confidentiality, integrity, and availability of the entire GitHub Enterprise Server instance.", "risk_and_exploitability": "The CVSS score of 8.1 reflects a high\u2011severity flaw. EPSS data is unavailable, but the vulnerability is not listed in CISA's KEV catalog, indicating no known widespread exploitation yet. Successful exploitation requires authenticated, privileged access to the GitHub Enterprise Server Management Console, meaning the attack surface is limited to administrators or compromised admin credentials. Even so, the impact of a successful attack is critical, providing full remote code execution on the server."}}}}, "created": "2026-04-22T03:45:06.829898+00:00", "updated": "2026-04-22T06:30:10.667268+00:00", "vendors": ["github", "github$PRODUCT$enterprise_server"]}