# CVE-2026-100865: Heym multiple RCE and authentication bypass vulnerabilities

Source: https://junglewise.ai/threats/cve-2026-100865-heym-before-0-0-53-contains-multiple-independent-vulnerabilities  
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-2026-100865 · Severity: high · CVSS 8.8 · Published 2026-09-27

Heym is a workflow automation platform. This advisory covers five independent vulnerabilities affecting versions before 0.0.53: unauthenticated webhook triggers, insecure OAuth handling, plaintext token storage, and Python code execution in workflow conditions. Attackers can execute arbitrary code as the backend user, hijack webhook authentication to trigger workflows with owner privileges, intercept OAuth tokens via malicious redirects, or exploit database leaks to obtain long-lived access tokens.

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

## Quick answers

**Is CVE-2026-100865 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100865 being exploited in the wild.

**How severe is CVE-2026-100865?** High severity, with a CVSS score of 8.8, published 27 September 2026.

**Which products and versions are affected?** Heymrun Heym before 0.0.53.

**Is there a fix for CVE-2026-100865?** A patch was published on 2026-09-27: version 0.0.53 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-100865 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-100865?** 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 workflow condition evaluator uses unsafe Python eval() without effective sandboxing (CWE-94), reachable by any user editing workflow conditions. Slack and Telegram webhook signature verification fails open when credentials or secrets are absent (CWE-287), allowing unauthenticated trigger activation. OAuth redirect_uri scheme validation is missing (CWE-601), permitting javascript: and data: URIs that intercept authorization codes and execute XSS in the Heym origin. Bearer tokens (WorkflowExecutionToken, PortalSession, HITLRequest.public_token, OAuthAuthorizationCode) are stored in plaintext (CWE-312), exposing valid scoped tokens with 168-hour TTL via database compromise.

## Affected products

- heymrun Heym before 0.0.53

## Timeline

- 2026-09-27: disclosed
- 2026-09-27: patched: version 0.0.53

## References

- [https://github.com/heymrun/heym/security/advisories/GHSA-pm6h-x3h5-j38h](https://github.com/heymrun/heym/security/advisories/GHSA-pm6h-x3h5-j38h)
- [https://www.vulncheck.com/advisories/heym-before-0.0.53-multiple-rce-and-authentication-bypass-vulnerabilities](https://www.vulncheck.com/advisories/heym-before-0.0.53-multiple-rce-and-authentication-bypass-vulnerabilities)

## Related threats

- [Heym privilege escalation via error_workflow_id field](https://junglewise.ai/threats/cve-2026-110873-heym-from-0-0-55-before-0-0-121-contains-a-privilege-escalation)
- [Heym token leakage in HITL review links via header spoofing](https://junglewise.ai/threats/cve-2026-105396-heym-before-v0-0-112-contains-a-token-leakage-vulnerability-in)
- [Heym Telegram webhook auth bypass](https://junglewise.ai/threats/cve-2026-101050-heym-before-0-0-53-fails-to-verify-the-x-telegram-bot-api-secret)
- [Heym authentication bypass in Slack webhook verification](https://junglewise.ai/threats/cve-2026-101049-heym-before-0-0-53-fails-to-verify-slack-request-signatures-when)
- [heym SSRF in credential-supplied base URLs](https://junglewise.ai/threats/cve-2026-100861-heym-before-0-0-105-fails-to-apply-egress-guards-to-integration)