CVE-2026-55438 coder vulnerability
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without confirming the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname. Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity. No known workarounds are available.
Quick answer
coder should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Review vendor advisory for affected versions.
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-55438 affects Coder remote development deployments before the patched Coder releases. The practical risk is origin or host-header trust issues in Coder workspace app routing that can expose app data across trust boundaries. Prioritize deployments with wildcard workspace app hostnames, shared app access, or upstream proxies that pass client-controlled forwarding headers. Coder fixed this issue in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2; deploy the matching patched branch or a later supported release. Where the advisory lists a workaround, apply it only as a temporary control until the patched version is deployed.
- Inventory all Coder server, CLI, provisioner, AI Bridge Proxy, workspace app proxy, and template-author deployments across production, staging, and developer environments.
- Identify affected Coder versions and compare each deployment against the fixed releases: 2.29.17, 2.32.7, 2.33.8, and 2.34.2, or a later supported release.
- Upgrade Coder servers and related components to the patched release for the installed branch, then roll out updated CLI binaries to users and automation hosts where the CLI is affected.
- Ensure upstream proxies strip or overwrite X-Forwarded-Host from untrusted clients and restrict wildcard app routing until patched.
- Review role bindings, template-author privileges, provisioner daemon access, wildcard app hostname exposure, and reverse proxy header handling for unnecessary trust.
- Review proxy logs, workspace app access, and CORS failures for crafted hostnames or unexpected X-Forwarded-Host values.
- If exploitation or credential exposure is suspected, revoke affected sessions, rotate tokens and credentials, preserve audit logs, and rebuild affected workspaces or hosts where integrity cannot be trusted.
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Verify the fix
- Confirm every Coder component reports a patched version: 2.29.17, 2.32.7, 2.33.8, and 2.34.2, or a later supported release for that branch.
- Confirm Coder resolves workspace app routing from trusted host identity and validates same-owner decisions against authoritative ownership.
- Validate proxy, wildcard app hostname, template, provisioner, and workspace permission settings against the intended least-privilege policy.
- Review Coder audit logs, reverse proxy logs, and workspace telemetry for exploitation attempts before and after patching.
- Document patched versions, changed settings, residual exceptions, and evidence, then rerun Fixnx or the relevant vulnerability scan where applicable.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-55438?
coder should be checked against the vendor advisory and trusted references linked on this page.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.