CVE-2026-100858 heym before 0.0.109 Server-Side Request Forgery via Workflow Nodes
An attacker can exploit SSRF in heym workflow nodes to access internal network resources and cloud metadata by using unvalidated URLs in credentials.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-100858?
CVE-2026-100858 is a high-severity server-side request forgery vulnerability in heymrun heym, published on 27 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
heym before 0.0.109 contains a server-side request forgery vulnerability in the Slack, Discord, and Crawler workflow nodes. These nodes issue HTTP requests to URLs taken from user-created credentials (webhook_url / flaresolverr_url) using an unguarded HTTP client, bypassing the SSRF egress guard that already protects the HTTP, WebSocket, and MCP nodes; the credential API validates only that the URL is non-empty. Any registered user can create a credential pointing at an internal address and execute a workflow, causing the backend to reach loopback, private, link-local, or cloud-metadata endpoints and return the full response body in the node output (non-blind SSRF).
Weakness: CWE-918
Which versions are affected by CVE-2026-100858?
How do I fix CVE-2026-100858?
No fix has been published for CVE-2026-100858 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-100858 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100858 exists.
Sources
Also known as GHSA-39j3-6x3x-8rcr, GHSA-68x6-m7x2-mcgw.