CVE-2026-100863 Heym before 0.0.91 SSRF via image fetching and IPv6 validation
Attackers can exploit SSRF flaws in Heym to access internal network resources and cloud metadata via image fetching and IPv6 validation bypasses.
- 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-2026-100863?
CVE-2026-100863 is a medium-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 versions 0.0.90 and earlier contain two server-side request forgery (SSRF) egress gaps, both remediated in app/services/ssrf_guard.py in 0.0.91. First, the LLM image-edit input loader (_load_image_bytes) fetched caller-controlled HTTP/HTTPS URLs with a bare httpx.get, applying only a scheme check and bypassing the egress-pinning HTTP client; because the workflow DSL supports "imageInput": "$userInput.body.imageUrl", a webhook or API caller can choose the fetch target when a workflow author uses that expression, allowing requests to loopback, RFC1918, and cloud metadata endpoints. Second, _is_public_address unwrapped only IPv4-mapped IPv6 addresses, so IPv6 transition forms — the NAT64 well-known prefix 64:ff9b::/96, deprecated IPv4-compatible ::x.x.x.x addresses, and 6to4 (2002::/16, classified as globally routable by Python 3.11.0 through 3.11.9) — could carry loopback, RFC1918, link-local, or cloud-metadata IPv4 destinations past both the initial URL validation and the dial-time IP pin. Version 0.0.91 routes the image loader through guard_http_url and the guarded client, evaluates NAT64 and IPv4-compatible addresses by their embedded IPv4 address, and refuses 64:ff9b:1::/48, 6to4, and Teredo (2001::/32) outright.
Weakness: CWE-918
Which versions are affected by CVE-2026-100863?
How do I fix CVE-2026-100863?
No fix has been published for CVE-2026-100863 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-2026-100863 being exploited?
There is no known exploitation of CVE-2026-100863 in the wild and no public exploit code.
Sources
Also known as GHSA-6rph-qqcv-jqh4, GHSA-j62x-q9gf-62p4.