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Coder vulnerable to SSH config injection via unsanitized server-supplied values in `coder config-ssh`

High severity GitHub Reviewed Published Jun 12, 2026 in coder/coder • Updated Jul 6, 2026

Package

gomod github.com/coder/coder/v2 (Go)

Affected versions

>= 2.34.0, < 2.34.2
>= 2.33.0, < 2.33.8
>= 2.30.0, < 2.32.7
< 2.29.17

Patched versions

2.34.2
2.33.8
2.32.7
2.29.17

Description

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!

References

@jdomeracki-coder jdomeracki-coder published to coder/coder Jun 12, 2026
Published to the GitHub Advisory Database Jul 6, 2026
Reviewed Jul 6, 2026
Last updated Jul 6, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(37th percentile)

Weaknesses

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. Learn more on MITRE.

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. Learn more on MITRE.

CVE ID

CVE-2026-55427

GHSA ID

GHSA-mcqq-fqgf-rxwm

Source code

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