Heym CVE-2026-84207

Exploitation requires a valid authenticated user account on the Heym instance with permission to create or modify workflow nodes (CVSS PR:L). The attacker must be able to place a WebSocket Send or WebSocket Trigger node with an arbitrary ws:// or wss:// URL into a workflow and trigger its execution. This condition is most consequential in multi-tenant or hosted Heym deployments where untrusted users hold workflow-authoring rights - the threat model the codebase explicitly identifies in ssrf_guard.py. Self-hosted single-tenant deployments with only trusted administrators are not at meaningful incremental risk. Exploitation is limited to WebSocket-scheme URLs; the HTTP node already had SSRF protection before this patch. No special server-side configuration is needed - the WebSocket guard was simply absent in all default deployments prior to v0.0.98.

The provided CVSS 4.0 score of 5.3 (Medium) appropriately reflects the authenticated, limited-impact nature of the flaw: PR:L confirms a valid user account is required, and VC:L/VI:L captures read-and-write access to internal services without full system compromise. EPSS data is absent from the provided intelligence, and this CVE is not listed in CISA KEV, so there is no confirmed evidence of active or widespread exploitation. No public POC has been identified. Real-world risk is substantially higher in multi-tenant or hosted Heym deployments - a threat scenario the codebase itself explicitly calls out in ssrf_guard.py comments - where untrusted authenticated users hold workflow-authoring permissions. In cloud-hosted deployments, reachability of the instance metadata service (169.254.169.254) elevates practical impact significantly, as successful SSRF there can yield IAM credentials. Self-hosted, single-tenant instances with fully trusted users face negligible additional risk beyond what already exists by trusting those users. The CVSS 4.0 subsequent-system metrics (SC:N/SI:N/SA:N) understate impact for cloud deployments where internal services may be materially affected.

An authenticated Heym user creates or edits a workflow and inserts a WebSocket Trigger node with the target URL set to ws://169.254.169.254/latest/meta-data/ or an internal microservice endpoint. When the workflow runs, the Heym backend opens a WebSocket connection to the internal target and surfaces the response through the node's output, delivering cloud IAM credentials or internal service data to the attacker. No public exploit code has been identified at time of analysis.