CVE-2026-100861: heym SSRF Vulnerability in Integration

CVE-2026-100861 Overview

CVE-2026-100861 is a Server-Side Request Forgery (SSRF) vulnerability [CWE-918] affecting heym versions prior to 0.0.105. The flaw stems from missing egress guards on integration services that accept credential-supplied base URLs. Authenticated users can configure credentials pointing to loopback interfaces, private network ranges, or cloud metadata endpoints. The application then issues requests to those destinations and returns responses as workflow node output. Attackers use this behavior to read internal service data that should remain inaccessible from user-controlled contexts.

Critical Impact
Authenticated attackers can bypass SSRF protections to reach internal services and cloud metadata endpoints, exposing confidential data through workflow node output.

Affected Products

heym versions before 0.0.105
Integration services within heym that accept credential-supplied base URLs
Workflow nodes consuming responses from credential-configured endpoints

Discovery Timeline

2026-09-27 - CVE-2026-100861 published to NVD
2026-09-28 - Last updated in NVD database

Technical Details for CVE-2026-100861

Vulnerability Analysis

The vulnerability resides in heym's integration subsystem, which allows authenticated users to configure third-party service credentials that include a base URL. The application performs HTTP requests to these URLs when workflows execute. Egress validation controls that would normally block requests to internal network destinations are not applied to this code path. The responses from these requests are returned as workflow node output, giving the attacker a direct read primitive against internal services.

This is a classic SSRF pattern made more impactful by two factors: the response body is reflected back to the user, and the attacker controls the destination through a legitimate configuration surface. Common targets include cloud metadata services on 169.254.169.254, internal admin APIs bound to loopback, and private-range services used for inter-service communication.

Root Cause

The root cause is incomplete enforcement of SSRF egress filtering. While heym likely applies destination restrictions on direct user-input URLs, the integration service abstraction treats credential-supplied base URLs as trusted configuration data. No validation prevents the base URL from pointing to loopback (127.0.0.0/8), private networks (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), link-local (169.254.0.0/16), or other reserved ranges.

Attack Vector

An authenticated user creates or edits an integration credential and sets the base URL to an internal target such as http://169.254.169.254/latest/meta-data/ or http://127.0.0.1:admin-port/. The attacker then triggers a workflow that uses the integration. The heym server issues the outbound request from its own network position and returns the response body as workflow node output visible to the attacker.

The vulnerability requires valid authentication and credential configuration permissions. See the GitHub Security Advisory GHSA-xchj-mw74-2232 and the VulnCheck SSRF Advisory for Heym for additional technical context.

Detection Methods for CVE-2026-100861

Indicators of Compromise

Outbound HTTP requests from the heym server process to 169.254.169.254, 127.0.0.0/8, or RFC1918 private ranges that do not correspond to legitimate backend services.
Integration credentials with base URLs referencing loopback, link-local, or private network addresses.
Workflow execution logs showing unexpected node output containing cloud metadata fields, internal API responses, or private service banners.

Detection Strategies

Audit the integration credential store for base URLs pointing to non-public destinations and flag any entries matching reserved IP ranges or localhost variants.
Inspect application and proxy logs for requests originating from the heym service to internal addresses outside the expected backend topology.
Correlate workflow execution events with outbound request destinations to identify SSRF probing patterns.

Monitoring Recommendations

Deploy egress monitoring that alerts when the heym host contacts cloud metadata endpoints or reserved IP ranges.
Enable detailed logging of integration credential create and update events, including the configured base URL.
Baseline normal workflow network behavior and alert on deviations such as new internal destinations or high-volume probing.

How to Mitigate CVE-2026-100861

Immediate Actions Required

Upgrade heym to version 0.0.105 or later, which applies egress guards to integration services.
Review all existing integration credentials and remove or correct any whose base URL points to internal, loopback, or metadata addresses.
Restrict permissions for creating and editing integration credentials to a minimum set of trusted administrators.

Patch Information

The maintainers addressed the issue in heym 0.0.105 by applying egress guards to the integration service code path so that credential-supplied base URLs are validated against the same SSRF protection rules used elsewhere in the application. Refer to the GitHub Security Advisory GHSA-xchj-mw74-2232 for the authoritative fix reference.

Workarounds

Place the heym server behind an egress proxy or firewall rule set that blocks outbound traffic to 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, and 169.254.0.0/16.
On cloud deployments, enforce IMDSv2 and require session tokens on 169.254.169.254 to blunt metadata exfiltration if a request leaks through.
Temporarily disable or restrict the integration feature until the upgrade is applied.

bash

# Example egress restriction using iptables on the heym host
iptables -A OUTPUT -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -d 127.0.0.0/8 ! -o lo -j REJECT
iptables -A OUTPUT -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -d 192.168.0.0/16 -j REJECT