The vulnerability stems from an Incorrect Authorization (CWE-863) flaw that permits peer‑ or session‑scoped API key holders to call the POST /v3/workspaces endpoint with a parent workspace name. The get_or_create_workspace routine verifies only the workspace claim, ignoring the owner's scope, which leads to the disclosure of workspace metadata and configuration such as custom_instructions that should be restricted to workspace or admin keys. This flaw facilitates the theft of sensitive configuration data without requiring privileged credentials.

Plastic Labs Honcho version 3.3.0 and earlier. The affected product is the Honcho API server hosted by Plastic Labs. Versions newer than 3.3.0 are presumed fixed, but the exact upstream fix version is not listed in the data.

The CVSS score of 5.3 indicates a medium severity. No EPSS score is provided, and the vulnerability is not listed in the CISA KEV catalog, suggesting it is not currently known to be exploited in the wild. The attack vector is likely remote, requiring the ability to send HTTP requests to the API and possession of a peer‑ or session‑scoped API key. Once the key is in hand, the attacker can send a crafted payload to POST /v3/workspaces and retrieve confidential workspace details, creating a moderate risk of data exposure so long as the API key can be obtained by adversaries.