CVE-2026-1999

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This issue only affected repositories that allow forking as the attack relies on opening a pull request from an attacker-controlled fork into the target repository. Exploitation was only possible in specific scenarios. It required a clean pull request status and only applied to branches without branch protection rules enabled. This vulnerability affected GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11, and was fixed in versions 3.19.2, 3.18.5, and 3.17.11. This vulnerability was reported via the GitHub Bug Bounty program."}, {"lang": "es", "value": "Una vulnerabilidad de autorizaci\u00f3n incorrecta fue identificada en GitHub Enterprise Server que permit\u00eda a un atacante fusionar su propia solicitud de extracci\u00f3n en un repositorio sin tener acceso de env\u00edo al explotar una omisi\u00f3n de autorizaci\u00f3n en la mutaci\u00f3n enable_auto_merge para solicitudes de extracci\u00f3n. Este problema solo afect\u00f3 a los repositorios que permiten la bifurcaci\u00f3n, ya que el ataque se basa en abrir una solicitud de extracci\u00f3n desde una bifurcaci\u00f3n controlada por el atacante en el repositorio objetivo. La explotaci\u00f3n solo fue posible en escenarios espec\u00edficos. Requer\u00eda un estado de solicitud de extracci\u00f3n limpio y solo se aplicaba a ramas sin reglas de protecci\u00f3n de rama habilitadas. Esta vulnerabilidad afect\u00f3 a las versiones de GitHub Enterprise Server anteriores a 3.19.2, 3.18.5 y 3.17.11, y fue corregida en las versiones 3.19.2, 3.18.5 y 3.17.11. 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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.17.0,3.17.11)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.18.0,3.18.5)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.19.0,3.19.2)"}}], "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": "2026-04-15T15:46:28.308060+00:00", "value": {"mitigation_remediation": ["Upgrade GitHub Enterprise Server to version 3.19.2 or later, 3.18.5 or later, or 3.17.11 or later.", "Disable repository forking for critical repositories until the patch is applied to reduce the attack surface.", "Enable or enforce branch protection rules and disable auto-merge for forks to prevent unauthorized merges."], "summary": {"action": "Apply Patch", "impact": "Unauthorized Code Integration"}, "threat_synthesis": {"affected_systems": "GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11 are affected. Updates to 3.19.2, 3.18.5, and 3.17.11 contain the fix.", "description_and_impact": "An incorrect authorization flaw in GitHub Enterprise Server allows an attacker to merge a pull request from an attacker-controlled fork into a target repository without having push rights. The vulnerability is triggered via the enable_auto_merge mutation for pull requests and is limited to situations where the repository allows forking, the pull request is clean, and there are no branch protection rules in place. This bypass permits the insertion of arbitrary code or configuration changes into the repository, potentially compromising the integrity of the codebase and downstream deployments. The weakness reflects an authorization bypass (CWE\u2011863).", "risk_and_exploitability": "The vulnerability carries a CVSS base score of 7.1, indicating high severity. The EPSS score is less than 1%, showing a low probability of exploitation, and it is not listed in the CISA KEV catalog. Exploitability requires a forking\u2011capable user, a clean pull request, and the absence of protected branches, which limits the attack surface but still allows a determined adversary to inject code into repositories that accept forks."}}}}, "created": "2026-02-19T10:11:16.956771+00:00", "updated": "2026-04-15T17:15:10.605961+00:00", "vendors": ["github", "github$PRODUCT$enterprise_server"]}