GHSA-mcqq-fqgf-rxwm: Coder vulnerable to SSH config injection via unsanitized server-supplied values in `coder config-ssh`

Summary coder config-ssh wrote server-supplied SSH settings (HostnameSuffix, SSHConfigOptions) into the user's ~/.ssh/config without sanitizing embedded newlines or restricting directives so a malicious or compromised Coder server could inject arbitrary SSH configuration. Note: Practical exploitation requires control of the server-supplied values through a malicious or compromised deployment, a man-in-the-middle position or admin access to the HostnameSuffix and SSHConfigOptions settings. Impact A server administrator or an attacker who controlled the server, could inject a directive such as ProxyCommand and achieve arbitrary code execution on any developer workstation that ran coder config-ssh. Injected commands ran with the local user's privileges and applied to all SSH connections, not just Coder workspaces. Patches The fix validates HostnameSuffix and SSHConfigOptions against a strict character set that rejects newlines and other control characters. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | v2.34.2 | | 2.33 | v2.33.8 | | 2.32 | v2.32.7 | | 2.29 (ESR) | v2.29.17 | Workarounds Inspect coder config-ssh --dry-run output before applying changes. Resources - Fix: #26154 Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22437) for independently disclosing this issue!