Coder's command line tool can open external workspace-app URLs without validating the URL's scheme or host. When a URL contains the $SESSION_TOKEN placeholder, the CLI substitutes it with the current user's session token before delegating the URL to the operating-system handler. This flaw allows a malicious external app definition, controlled by a template author, to expose the user's authentication credential to an arbitrary host or scheme; the possibility that this could be used for account impersonation is inferred from the fact that the session token grants authenticated access, but this is not explicitly stated. The vulnerability is a sensitive information exposure (CWE-522) that also functions like an open-redirect (CWE-601).

Versions of coder:coder before 2.29.7, 2.32.7, 2.33.8, or 2.34.2 are affected. Workspaces whose external app URLs can be configured by a template author or attacker are impacted. Any organization provisioning such workspaces with the vulnerable CLI is at risk.

The CVSS base score of 7.7 indicates high severity, while the EPSS score of less than 1% reflects a low but nonzero likelihood of exploitation. The issue is not listed in the CISA KEV catalog. Exploitation requires the victim to run coder open app on a workspace with an attacker-controlled external app URL, so the attack vector is local to invoke the command.