The vulnerability is a server‑side request forgery that allows an unauthenticated attacker to direct the Manage API to send crafted outbound requests to an attacker‑controlled host. An unauthenticated endpoint parses an attacker‑supplied cluster configuration and issues gateway‑to‑agent requests whose HMAC authenticates only a timestamp, not the request path or body. An attacker who intercepts the outbound request can capture the bearer token and replay it against privileged management‑agent endpoints, effectively allowing the attacker elevated control of the GitHub Enterprise Server infrastructure. High‑availability deployments are not impacted because the topology restriction prevented the exploit.

Affected are GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, and 3.21 series. The vulnerability was fixed in the patch releases 3.17.21, 3.18.15, 3.19.12, 3.20.8, and 3.21.6. High‑availability deployments are not affected because the vulnerability relies on a topology restriction that does not apply to HA setups.

The CVSS score of 8.2 indicates high severity. The EPSS score is < 1%, suggesting a low probability of exploitation at present. The vulnerability is not listed in the CISA KEV catalog. The exploit requires an unauthenticated Manage API endpoint that accepts a crafted cluster configuration, followed by the ability to intercept the gateway‑to‑agent request. Once intercepted, the bearer token can be replayed against privileged management‑agent endpoints, giving the attacker elevated control over the GitHub Enterprise Server infrastructure. The realistic attack vector likely involves sending malicious requests to the vulnerable endpoint and then capturing the outbound traffic, before replaying the token to privileged endpoints. High‑availability deployments are not susceptible because the topology restriction prevents the exploit.