Heym EUVD-2026-101756

Exploitation requires that the attacker already hold shared-collaborator access to the target workflow (PR:L) and that Heym's workflow-sharing/collaboration feature be in use - a single-owner deployment with no shared collaborators is not exposed. The specific prerequisite is that the error_workflow_id field is omitted from OWNER_ONLY_EXECUTION_FIELDS, letting a non-owner collaborator set it to a workflow they control; the attacker must then supply an error workflow containing an HTTP (or similar outbound) node and cause the parent workflow to error so the owner's decrypted credentials are injected and sent out. Limiting factors: existing collaborator privilege is mandatory, the parent workflow must actually enter an error state, and the owner's workflow must have stored credentials worth stealing. Affected only in versions 0.0.55 through before 0.0.121.

The supplied CVSS 4.0 vector (CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N, base 7.1 High) describes a network-reachable, low-complexity attack that requires low privileges (PR:L) and no user interaction, with high confidentiality impact (VC:H) and only low integrity impact (VI:L) from overwriting a single field. The PR:L metric is the decisive risk-limiter: the attacker must already be a legitimately shared collaborator on the victim's workflow, so this is not an unauthenticated internet-wide mass-exploitation condition - it is an insider/abuse-of-trust escalation within a multi-tenant or team deployment. No EPSS score, SSVC decision, KEV listing, or POC indicator was provided in the input, so exploitation probability and automatability cannot be quantified from the data; per the input signals this is 'no public exploit identified at time of analysis.' Net assessment: this is a genuine high-severity credential-theft flaw for organizations that use Heym's workflow sharing/collaboration feature, but real-world urgency is tempered by the collaborator-access prerequisite and the absence of any exploitation or POC telemetry in the provided sources. MISSING DATA: EPSS, KEV, POC, and SSVC fields were all absent from the input and could not be weighed.

A user who has been granted shared-collaborator access to a victim's Heym workflow edits the workflow's error_workflow_id (a field the authorization layer fails to protect) to point at a malicious workflow they control containing an HTTP node. When the parent workflow subsequently errors - which the attacker can often induce - Heym injects the owner's decrypted credentials into the attacker's error workflow, and the HTTP node exfiltrates them to an attacker-controlled endpoint. No public exploit code was identified at time of analysis, so this reflects the mechanism described in the advisory rather than a confirmed in-the-wild technique.