CVE-2026-55427: Coder vulnerable to SSH config injection via unsanitized server-supplied values in `coder config-ssh`

Severity: high (CVSS 8.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-08 · updated 2026-07-08
Weakness: CWE-74

Description

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, `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. 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. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 validates `HostnameSuffix` and `SSHConfigOptions` against a strict character set that rejects newlines and other control characters. As a workaround, inspect `coder config-ssh --dry-run` output before applying changes.

Affected products

coder: before 2.29.17; from 2.30.0 before 2.32.7; from 2.33.0 before 2.33.8; from 2.34.0 before 2.34.2 — fixed in 2.29.17, 2.32.7, 2.33.8, 2.34.2

How to fix

Upgrade to a fixed version: coder 2.29.17, 2.32.7, 2.33.8, 2.34.2. Check the vendor advisory for mitigations.

References

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