CVE-2026-100863
Received Received - Intake

SSRF Egress Gaps in Heym Versions 0.0.90 and Earlier

Publication date: 2026-09-27

Last updated on: 2026-09-27

Assigner: VulnCheck

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.

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Meta Information

Published
2026-09-27
Last Modified
2026-09-27
Generated
2026-09-27
AI Q&A
2026-09-27
EPSS Evaluated
N/A
NVD
CVE-2026-100863
EUVD
EUVD-2026-87828

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
heym heym to 0.0.91 (exc)
heym heym 0.0.91

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

Attack-Flow Graph

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Executive Summary

CVE-2026-100863 involves two Server-Side Request Forgery (SSRF) vulnerabilities in the heym application affecting versions up to 0.0.90. The first allows attackers to bypass SSRF protections when fetching images via an unguarded HTTP client that fetches caller-controlled URLs. The second involves IPv6 address validation where certain transition addresses could embed internal IPv4 addresses and bypass protections.

Detection Guidance

To detect this vulnerability, check if your heym instance is running a version earlier than 0.0.91. Use commands like 'heym --version' or inspect the application logs for version information. Monitor network traffic for unexpected outbound requests to internal or cloud metadata endpoints, especially from the image fetching component.

Impact Analysis

An attacker could exploit these SSRF flaws to access internal network resources, loopback addresses, private IP ranges, or cloud metadata endpoints. This could lead to unauthorized data exposure, service disruption, or further network infiltration depending on the targeted systems.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling unauthorized access to internal or restricted resources through SSRF attacks. Attackers could exploit these flaws to fetch sensitive data from loopback, private, or cloud metadata endpoints, which may include personal data protected under GDPR or protected health information under HIPAA.

Mitigation Strategies

Upgrade heym to version 0.0.91 or later immediately. If upgrading is not possible, disable the image fetching feature or restrict outbound network access to trusted endpoints. Review and enforce strict SSRF protections, including URL validation, IP pinning, and blocking IPv6 transition addresses like NAT64, 6to4, and Teredo.

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