CVE-2026-55427

### 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](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/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!