# CVE-2026-100859: Heym credential exfiltration in credentials test endpoint

Source: https://junglewise.ai/threats/cve-2026-100859-heym-before-0-0-106-contains-a-credential-exfiltration  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-27. Updated: 2026-09-27  
License: CC BY 4.0 with a link back

CVE-2026-100859 · Severity: medium · CVSS 6.5 · Published 2026-09-27

Heym is a credential management platform that allows teams to securely store and share authentication secrets. A flaw in the credential testing endpoint allows a collaborator with legitimate access to a shared credential to steal the credential owner's authentication secret by redirecting the test request to an attacker-controlled server. This enables unauthorized disclosure of sensitive credentials like API tokens and passwords.

Technologies: [Heymrun Heym](https://junglewise.ai/threats/technologies/heym). Vendors: [Heymrun](https://junglewise.ai/threats/vendors/heymrun).

## Quick answers

**Is CVE-2026-100859 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100859 being exploited in the wild.

**How severe is CVE-2026-100859?** Medium severity, with a CVSS score of 6.5, published 27 September 2026.

**Which products and versions are affected?** Heymrun Heym before 0.0.106.

**Is there a fix for CVE-2026-100859?** A patch was published on 2026-09-05: Fix released in version 0.0.106 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-100859 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-100859?** Check whether you run Heymrun Heym at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The POST /api/credentials/test endpoint improperly validates configuration overrides, allowing an authenticated collaborator to merge caller-supplied config (including a malicious base_url) with a shared credential before testing the connection. The endpoint then sends the decrypted credential's authentication secret to the attacker-specified URL via integrations like Jira and Supabase. An attacker must have legitimate shared access to a credential and network access to call the endpoint.

## Affected products

- heymrun Heym before 0.0.106

## Timeline

- 2026-09-05: disclosed: GitHub security advisory published
- 2026-09-05: patched: Fix released in version 0.0.106

## References

- [https://github.com/heymrun/heym/security/advisories/GHSA-39qx-wp7x-69rq](https://github.com/heymrun/heym/security/advisories/GHSA-39qx-wp7x-69rq)
- [https://www.vulncheck.com/advisories/heym-before-0.0.106-credential-exfiltration-via-url-override](https://www.vulncheck.com/advisories/heym-before-0.0.106-credential-exfiltration-via-url-override)

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