CVE-2026-100865
Received Received - Intake

Python Code Execution in Heym Workflow System

Publication date: 2026-09-27

Last updated on: 2026-09-27

Assigner: VulnCheck

Description
Heym before 0.0.53 contains multiple independent vulnerabilities. (1) The workflow condition evaluator uses Python eval() without an effective sandbox, allowing any user who can edit a workflow branch/condition node — or who can import a workflow template containing a malicious condition node — to execute arbitrary Python code as the backend process user when the workflow runs. (2) Slack webhook signature verification and (3) Telegram webhook secret-token verification fail open when the trigger node has no credentialId or an empty signing secret, allowing anyone who knows the public webhook URL to trigger workflows with the owner's credentials without authentication. (4) The OAuth authorization endpoint does not validate the redirect_uri scheme, so an attacker who registers a public OAuth client with a javascript: or data: redirect_uri and lures a victim to the consent screen receives the authorization code and executes attacker-controlled JavaScript in the Heym origin, including access to the victim's HttpOnly auth cookie. (5) WorkflowExecutionToken, PortalSession, HITLRequest.public_token, and OAuthAuthorizationCode values are stored in plaintext, so any database read exposure yields valid scoped bearer tokens, including portal and HITL tokens with a 168-hour TTL that permit workflow execution on behalf of the owner.

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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-2026-100865
EUVD
EUVD-2026-87830

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
heym heym 0.0.53
heym heym to 0.0.53 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-94 The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

Attack-Flow Graph

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Executive Summary

CVE-2026-100865 affects the heym application versions before 0.0.53 and includes multiple vulnerabilities. The most critical is a Remote Code Execution (RCE) flaw due to unsafe use of Python's eval() function in the workflow condition evaluator, allowing arbitrary code execution as the backend user. Other issues include authentication bypass via failed webhook signature verification for Slack and Telegram, an OAuth redirect_uri validation flaw enabling JavaScript execution and auth cookie theft, and plaintext storage of sensitive tokens like WorkflowExecutionToken and PortalSession.

Detection Guidance

Check Heym version with 'heym --version' or inspect package files. Look for workflow files containing eval() or webhook configurations without signature verification. Search for plaintext tokens in database backups or logs. Monitor for unauthorized workflow executions or unexpected Python code execution.

Impact Analysis

This vulnerability can lead to full account takeover, unauthorized workflow execution, and remote code execution on the backend system. Attackers could trigger workflows with your credentials, execute malicious Python code, steal authentication cookies, or gain access to sensitive tokens stored in plaintext, potentially allowing long-term unauthorized access.

Compliance Impact

This vulnerability likely violates compliance requirements for data protection and security. The plaintext storage of tokens and potential unauthorized access to sensitive workflows could lead to data breaches, violating GDPR's data protection principles and HIPAA's security rules for protected health information. The RCE and authentication bypasses further exacerbate compliance risks by enabling unauthorized system access.

Mitigation Strategies

Upgrade Heym to version 0.0.53 or later immediately. Disable workflow editing permissions for untrusted users. Remove or secure Slack/Telegram webhook URLs. Validate OAuth redirect_uri schemes strictly. Encrypt stored tokens and rotate all exposed credentials.

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