GitHub Enterprise Server up to 3.21.4 Pre-receive Hook server-side request forgery

Summaryinfo

A vulnerability categorized as critical has been discovered in GitHub Enterprise Server up to 3.17.19/3.18.13/3.19.10/3.20.6/3.21.4. This affects an unknown function of the component Pre-receive Hook. The manipulation results in server-side request forgery. This vulnerability is cataloged as CVE-2026-76851. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as critical has been found in GitHub Enterprise Server up to 3.17.19/3.18.13/3.19.10/3.20.6/3.21.4. Affected is an unknown functionality of the component Pre-receive Hook. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

A Server-Side Request Forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed remote code execution on the instance. Insufficient network isolation allowed malicious pre-receive hook code to impersonate an internal service and redirect trusted internal requests to a privileged service, leading to elevated code execution. Exploitation required pre-receive hook networking to be enabled and either site administrator privileges or write access to a repository containing a configured pre-receive hook. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.20, 3.18.14, 3.19.11, 3.20.7, and 3.21.5. This vulnerability was reported via the GitHub Bug Bounty program.

The advisory is shared for download at docs.github.com. This vulnerability is traded as CVE-2026-76851 since 08/19/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available.

Upgrading to version 3.17.20, 3.18.14, 3.19.11, 3.20.7 or 3.21.5 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-69716). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Bug Tracking Software

Vendor

• GitHub

Name

• Enterprise Server

Version

• 3.17.0
• 3.17.1
• 3.17.2
• 3.17.3
• 3.17.4
• 3.17.5
• 3.17.6
• 3.17.7
• 3.17.8
• 3.17.9
• 3.17.10
• 3.17.11
• 3.17.12
• 3.17.13
• 3.17.14
• 3.17.15
• 3.17.16
• 3.17.17
• 3.17.18
• 3.17.19
• 3.18.0
• 3.18.1
• 3.18.2
• 3.18.3
• 3.18.4
• 3.18.5
• 3.18.6
• 3.18.7
• 3.18.8
• 3.18.9
• 3.18.10
• 3.18.11
• 3.18.12
• 3.18.13
• 3.19.0
• 3.19.1
• 3.19.2
• 3.19.3
• 3.19.4
• 3.19.5
• 3.19.6
• 3.19.7
• 3.19.8
• 3.19.9
• 3.19.10
• 3.20.0
• 3.20.1
• 3.20.2
• 3.20.3
• 3.20.4
• 3.20.5
• 3.20.6
• 3.21.0
• 3.21.1
• 3.21.2
• 3.21.3
• 3.21.4

License

• open-source

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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