SSRF in Heymrun Heym
CVE-2026-100858
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).
Vulnerability class: SSRF (Server-Side Request Forgery)
Published .
CVSS v3 metric
CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/heymrun/heym/security/advisories/GHSA-39j3-6x3x-8rcr (vendor-advisory)
- www.vulncheck.com/advisories/heym-before-0.0.109-server-side-request-forgery-vi… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100858?
- CVE-2026-100858 is a medium-severity vulnerability in Heymrun Heym, classified under Server-Side Request Forgery (SSRF). CVSS score: 6.8/10. Published 2026-09-27.
- How severe is CVE-2026-100858?
- Medium severity. CVSS v3 base score is 6.8 out of 10.