GitHub Enterprise Server CVE-2026-104608

Requires an attacker-controlled account on the target instance with SSH access to the Git service (PR:L) - not anonymous or pre-auth. The trigger is a re-entrant callback invoked when babeld calls into the SSH library while holding references into an internal collection, which invalidates those references (use-after-free); this is reachable through normal authenticated Git-over-SSH operations rather than a non-default feature toggle. The principal limiting factors are that successful code execution requires per-build memory offsets (AC:H) and that failed attempts crash babeld, making exploitation unreliable and likely to produce detectable service outages. Affected: all GitHub Enterprise Server releases prior to 3.23; fixed in 3.22.3, 3.21.8, 3.20.10, and 3.19.14. Per the available sources, updating to a fixed release is the remediation; no alternative mitigation is stated.

This is a genuinely serious but practically gated vulnerability, not an inflated high-CVSS score. The CVSS 4.0 vector (AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H) scores 7.7 (High) and reflects full compromise of the babeld process - remote code execution plus disclosure of its environment secrets. Three factors meaningfully constrain real-world risk: PR:L means the attacker needs a valid account with SSH access to the instance (not anonymous), AC:H reflects that successful exploitation requires per-build memory offsets, and the description states that failed attempts crash babeld - making exploitation unreliable, noisy, and likely to generate detectable service disruption. No EPSS score was provided, the CVE is not in CISA KEV, and the only references are vendor release notes with no proof-of-concept, so there is no public exploit identified at time of analysis. The vuln.today decision label is 'this_week' (not act_now/emergency), consistent with a patch-promptly-but-not-drop-everything posture. Net: credible RCE on an exposed service, but the account requirement plus the fragile per-build-offset trigger make this a prioritized-patch item rather than an actively-exploited crisis. Key missing data: no EPSS, no independent CVSS from NVD shown, and no vendor advisory text beyond release-note anchors.

An attacker who already holds a GitHub Enterprise Server account with SSH access connects to the Git service and issues operations that drive babeld to invoke the SSH library, triggering a re-entrant callback that mutates an internal collection while babeld still holds references into it. By exploiting the resulting use-after-free as a controlled write - and having first determined the correct per-build memory offsets - the attacker runs arbitrary commands as the babeld service and reads its environment secrets. No public exploit code is identified at time of analysis, and because failed attempts crash babeld, a real attack would likely cause observable service instability.