CVE-2026-18730: github enterprise_server Server-Side Request Forgery (SSRF)

Vulnerability summary

CVE-2026-18730 is a high (CVSS 8.2) Server-Side Request Forgery (SSRF) vulnerability in github enterprise_server. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 20.3% of scored vulnerabilities.

Timeline

1. 01-09-2026
   PublishedVulnerability first disclosed.
2. 22-09-2026
   Last modifiedVulnerability information updated.

Description

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to cause the Manage API to send crafted outbound requests to an attacker-controlled host. An unauthenticated endpoint parsed an attacker-supplied cluster configuration and issued gateway-to-agent requests whose HMAC authenticated only a timestamp, not the request path or body. An attacker positioned to intercept the outbound request could capture this token and replay it against privileged management agent endpoints. High-availability deployments were not affected due to a topology restriction. This vulnerability affected GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, and 3.21 series and was fixed in versions 3.17.21, 3.18.15, 3.19.12, 3.20.8, and 3.21.6. This vulnerability was reported via the GitHub Bug Bounty program.

• CWE-918Server-Side Request Forgery (SSRF)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.