# 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.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** GHSA-6rph-qqcv-jqh4, GHSA-j62x-q9gf-62p4

## 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 (Server-Side Request Forgery)

## 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.

## Is CVE-2026-100863 being exploited?

There is no known exploitation of CVE-2026-100863 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100863 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-100863 in the wild and no public exploit code.

Affected product: heymrun heym. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100863/ (Markdown: https://insights.sbomify.com/CVE-2026-100863/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100863
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100863
- OSV: https://osv.dev/vulnerability/CVE-2026-100863

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100863/
Summaries are generated and may contain mistakes; the official description above is the record.