Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

Summary

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 open app` opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the `$SESSION_TOKEN` placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run `coder open app` against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits `$SESSION_TOKEN` substitution to trusted destinations like the web frontend. As a workaround, avoid running `coder open app` for untrusted workspaces.

Timeline

1. Jul 8, 2026, 12:10 AM UTCCVE published
2. Jul 8, 2026, 1:56 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Jul 8, 2026, 1:57 PM UTCRecord last updated

Affected versions

• coder coder

  From 2.34.0 · fixed in 2.34.2; From 2.33.0 · fixed in 2.33.8; From 2.30.0 · fixed in 2.32.7; fixed in 2.29.17

• github.com/coder/coderGo

  All versions

• github.com/coder/coder/v2Go

  fixed in 2.29.17; From 2.30.0 · fixed in 2.32.7; From 2.33.0 · fixed in 2.33.8; From 2.34.0 · fixed in 2.34.2

• github.com/coder/coder/v2Go

  From 2.34.0 · fixed in 2.34.2

• github.com/coder/coder/v2Go

  From 2.33.0 · fixed in 2.33.8

• github.com/coder/coder/v2Go

  From 2.30.0 · fixed in 2.32.7

• github.com/coder/coder/v2Go

  fixed in 2.29.17

References 6