CVE-2026-18730

A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program.

GitHub Enterprise Server before version 3.22 has a path traversal vulnerability that allows an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. Exploitation of the X-GitHub-Request-Id header without sanitization as a filesystem path segment leads to data deletion.

GitHub Enterprise Server prior to version 3.22 has an SSRF vulnerability in an upload endpoint that allows an unauthenticated attacker to send crafted requests to internal services. By injecting path traversal content into request parameters, an attacker can bypass the intended request flow and redirect internal API calls.

GitHub Enterprise Server has an improper input neutralization vulnerability enabling DOM-based cross-site scripting via the Issues search label filter, which could lead to privilege escalation and unauthorized workflow triggers. Exploitation requires access to the instance and enticing a user in sudo mode to click a crafted malicious link.

An out-of-bounds read vulnerability was identified in GitHub Enterprise Server in the Git service (babeld). When proving possession of a host key, babeld's SSH implementation sized the session identifier by the current digest length rather than its own. An attacker with an account and SSH access could re-key to an algorithm with a longer hash, causing adjacent process memory to be signed and returned to the client, where a limited amount may be recoverable. The vulnerability affected all releases prior to 3.23 and was fixed in versions 3.22.3, 3.21.8, 3.20.10, and 3.19.14.

A cross-site request forgery vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete stored Slack and Microsoft Teams ChatOps configuration and provider credentials by inducing an authenticated Management Console operator's browser to send a cross-site GET request to the integration removal endpoint without a CSRF token. Exploitation required configured ChatOps integrations and an operator visiting attacker-controlled content while signed in. The vulnerability affected all versions of GitHub Enterprise Server prior to 3.23 and was fixed in versions 3.19.14, 3.20.10, 3.21.8, and 3.22.3.

A use-after-free remote code execution vulnerability was identified in GitHub Enterprise Server in the Git service (babeld). An attacker with an account and SSH access could leverage it into a controlled write and run arbitrary commands as babeld, including disclosure of environment secrets. It affected all releases prior to 3.23 and was fixed in 3.22.3, 3.21.8, 3.20.10, and 3.19.14.

A Server-Side Request Forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed a repository contributor to cause the appliance to issue requests to attacker-controlled internal hosts, which could be chained to achieve remote code execution on the appliance. The secret scanning validator for GCP service account credentials trusted the token endpoint embedded in a committed credential and issued a request to it without restricting the destination. Exploitation required an authenticated user with permission to push to a repository on an instance with GitHub Advanced Security and secret scanning validity checks enabled, a non-default configuration. This vulnerability affected GitHub Enterprise Server 3.20, 3.21, and 3.22 and was fixed in versions 3.20.9, 3.21.7, and 3.22.2. This vulnerability was reported through the GitHub Bug Bounty program.

A missing authorization vulnerability in GitHub Enterprise Server allowed a repository collaborator with write access to delete the current default branch via the GraphQL API and cause an attacker-controlled branch to become the new default. In repositories requiring pull-request review but not restricting branch deletion, this bypassed the review requirement and caused fresh clones and default-branch API requests to use attacker-controlled content.

A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user.