GitHub Enterprise Server: DOM-based XSS in the Issues label filter escalates privilege in sudo mode

Impact

A self-hosted GitHub Enterprise Server appliance is where many fleets keep the code, Actions workflows and deploy credentials that build and ship everything running on the GPU nodes. The Issues search label filter does not neutralize input, so a crafted link executes script in the victim's browser session against the appliance. If the victim is operating in sudo mode at the time, the script can perform actions that require elevated privileges and trigger workflows they did not intend, which on a CI host means attacker-chosen jobs running with the runners' credentials. Exploitation needs the attacker to have access to the instance and the victim to click the link, so this is an insider or foothold-stage escalation rather than an internet-facing takeover.

Who can reach it

Any authenticated user with access to the GHES instance, who must then get an administrator or other privileged user to click a crafted link while that user is in sudo mode.

What to do

Upgrade the appliance to 3.18.1, 3.17.7, 3.16.10, 3.15.14 or 3.14.19 as appropriate for the installed branch. GHES upgrades are an appliance maintenance window: the instance goes offline for the hotpatch or upgrade and CI that depends on it stalls for the duration. There is no documented configuration mitigation; until the upgrade, limit who can enter sudo mode and treat links into Issues search from untrusted users as suspect.

References

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