Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-55431
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 20:07 UTC · Revision 1
Source evidence
Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps
core-osv · Original sourcePublished 8 Jul 2026, 00:10 UTC
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.
osv:CVE-2026-55431
Complete source record
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"id": "b5b32b461c21b42b1b053976302782429cff551e1da9ffd22129768c325655e2",
"url": "https://osv.dev/vulnerability/CVE-2026-55431",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "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.",
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"provider": "osv",
"references": [
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"source_id": "core-osv",
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