GitHub fixes secret-scanning flaw that can reach code execution on GHES

GitHub fixes secret-scanning flaw that can reach code execution on GHES

6 October 2026: GitHub has patched CVE-2026-96890, a high-severity server-side request forgery in the secret-scanning validity checks of GitHub Enterprise Server that can lead to remote code execution on the appliance. A second flaw, CVE-2026-103620, rated medium, lets a repository collaborator replace the default branch. Fixes shipped in the 3.22.2 and 3.21.7 releases, and the second flaw is also fixed in 3.18.16. GitHub's notes do not describe exploitation in the wild.

Not yet independently verified. We read the release notes for 3.22.2, 3.21.7 and 3.18.16 only. The notes for 3.19.13 and 3.20.9 were not read, so which fix lands in which of those two is taken from the Hong Kong CERT summary. We will update this when it can be confirmed, and remove this note.

How the high-severity flaw works

An attacker commits crafted GCP service account credentials to a repository. When secret scanning runs its validity check on them, the appliance sends requests to addresses the attacker chose, without enough validation. GitHub says this could lead to remote code execution on the appliance. The attacker needs push access to a repository that has GitHub Advanced Security enabled, so the exposure sits with organisations that give many contributors push rights and have switched secret scanning on.

The default-branch bypass

CVE-2026-103620 involves the GraphQL API. A collaborator with write access could delete the default branch and make a branch under their control the new default. In repositories that require pull request review but do not restrict branch deletion, this skipped the review requirement, so fresh clones and default-branch API requests would receive the attacker's content. GitHub's 3.18.16 notes say the report came through its bug bounty programme.

Fixed versions

Hong Kong's CERT lists the fixed releases as:

• 3.22.2
• 3.21.7
• 3.20.9
• 3.19.13
• 3.18.16

The 3.22.2 and 3.21.7 notes list both CVEs. The 3.18.16 notes list one security fix, CVE-2026-103620. All the releases are dated 6 October.

Before upgrading

GitHub's known issues for these releases include custom firewall rules being removed during an upgrade, so they must be reapplied afterwards. The 3.18.16 notes also mention that Management Console lockouts do not unlock on their own and need SSH access to clear. Until a patch is in, restricting who can push to repositories with Advanced Security enabled, and restricting branch deletion where review rules matter, narrows both paths.

Company profile on TrustList: GitHub

Related on TrustList:

• GitLab AI Gateway flaw CVE-2026-90970 lets Duo Agent Platform users escape the sandbox and run commands: update self-hosted gateways
• GitHub Enterprise Cloud with data residency refuses X25519-only TLS clients from 7 October 2026

Sources

• GitHub Docs, GitHub Enterprise Server 3.22.2 release notes, 6 October 2026
• GitHub Docs, GitHub Enterprise Server 3.21.7 release notes, 6 October 2026
• GitHub Docs, GitHub Enterprise Server 3.18.16 release notes, 6 October 2026
• HKCERT, GitHub Enterprise Server Multiple Vulnerabilities, 8 October 2026