Summary
Coder vulnerable to SSH config injection via unsanitized server-supplied values in coder config-ssh
Full technical description
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.
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!
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.
Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.
CVE-2026-55427 has a CVSS score of 8.3 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.34.2, 2.33.8, 2.32.7, 2.29.17); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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:
Frequently Asked Questions
- What is CVE-2026-55427? CVE-2026-55427 is a high-severity OS command injection vulnerability in github.com/coder/coder/v2 (go), affecting versions >= 2.34.0, < 2.34.2. It is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
- How severe is CVE-2026-55427? CVE-2026-55427 has a CVSS score of 8.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/coder/coder/v2 are affected by CVE-2026-55427? github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.
- Is there a fix for CVE-2026-55427? Yes. CVE-2026-55427 is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Upgrade to this version or later.
- Is CVE-2026-55427 exploitable, and should I be worried? Whether CVE-2026-55427 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-55427 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-55427?
- Upgrade
github.com/coder/coder/v2to 2.34.2 or later - Upgrade
github.com/coder/coder/v2to 2.33.8 or later - Upgrade
github.com/coder/coder/v2to 2.32.7 or later - Upgrade
github.com/coder/coder/v2to 2.29.17 or later
- Upgrade