GitHub Enterprise Server up to 3.20.0 Notebook Rendering Service server-side request forgery

Summaryinfo

A vulnerability was found in GitHub Enterprise Server up to 3.20.0 and classified as critical. Affected by this vulnerability is an unknown functionality of the component Notebook Rendering Service. Such manipulation leads to server-side request forgery. This vulnerability is traded as CVE-2026-5921. The attack may be launched remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in GitHub Enterprise Server up to 3.20.0 and classified as critical. Affected by this issue is an unknown code of the component Notebook Rendering Service. The manipulation with an unknown input leads to a server-side request forgery vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.

The weakness was shared by R31n. The advisory is available at docs.github.com. This vulnerability is handled as CVE-2026-5921 since 04/08/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available.

Upgrading to version 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5 or 3.20.1 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Bug Tracking Software

Vendor

• GitHub

Name

• Enterprise Server

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.14.0
• 3.14.1
• 3.14.2
• 3.14.3
• 3.14.4
• 3.14.5
• 3.14.6
• 3.14.7
• 3.14.8
• 3.14.9
• 3.14.10
• 3.14.11
• 3.14.12
• 3.14.13
• 3.14.14
• 3.14.15
• 3.14.16
• 3.14.17
• 3.14.18
• 3.14.19
• 3.14.20
• 3.14.21
• 3.14.22
• 3.14.23
• 3.14.24
• 3.14.25
• 3.15
• 3.15.0
• 3.15.1
• 3.15.2
• 3.15.3
• 3.15.4
• 3.15.5
• 3.15.6
• 3.15.7
• 3.15.8
• 3.15.9
• 3.15.10
• 3.15.11
• 3.15.12
• 3.15.13
• 3.15.14
• 3.15.15
• 3.15.16
• 3.15.17
• 3.15.18
• 3.15.19
• 3.15.20
• 3.16
• 3.16.0
• 3.16.1
• 3.16.2
• 3.16.3
• 3.16.4
• 3.16.5
• 3.16.6
• 3.16.7
• 3.16.8
• 3.16.9
• 3.16.10
• 3.16.11
• 3.16.12
• 3.16.13
• 3.16.14
• 3.16.15
• 3.16.16
• 3.17
• 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
• 3.18
• 3.18.0
• 3.18.1
• 3.18.2
• 3.18.3
• 3.18.4
• 3.18.5
• 3.18.6
• 3.18.7
• 3.19
• 3.19.0
• 3.19.1
• 3.19.2
• 3.19.3
• 3.19.4
• 3.20.0

License

• open-source

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

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CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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