Heym — CraftedSignal Threat Feed

Heym Path Traversal Vulnerability in File Upload Endpoint (CVE-2026-45225)

hello@craftedsignal.io — Tue, 12 May 2026 22:22:11 +0000

Heym before version 0.0.21 contains a path traversal vulnerability in its file upload endpoint. This flaw allows authenticated users to write malicious files to arbitrary locations on the server. By crafting a filename containing traversal sequences (e.g., ../../), an attacker can bypass intended path restrictions and manipulate files outside of the designated upload directory. This vulnerability affects the upload_file() handler due to insufficient validation of the filename parameter. Successful exploitation could lead to arbitrary file write, read, or even deletion, potentially compromising the entire system.

Attack Chain

Attacker authenticates to the Heym application.
Attacker crafts a malicious filename containing path traversal sequences (e.g., ../../../evil.php).
Attacker initiates a file upload request to the upload_file() endpoint, including the crafted filename.
The upload_file() handler receives the request but fails to properly sanitize the filename.
The application writes the uploaded file to a location outside the intended directory, based on the path provided in the crafted filename.
The attacker triggers execution of the uploaded file (e.g. if it’s a PHP file).
The attacker achieves arbitrary code execution on the server.

Impact

Successful exploitation of this vulnerability allows an attacker to write, read, or delete files outside the intended storage directory. This can lead to arbitrary code execution, allowing the attacker to gain complete control over the affected system. The CVSS v3.1 base score for this vulnerability is 7.6 (High), indicating a significant risk. The potential impact includes unauthorized access to sensitive data, modification of critical system files, and complete system compromise.

Recommendation

Upgrade Heym to version 0.0.21 or later to patch CVE-2026-45225.
Implement robust filename validation and sanitization within the upload_file() handler to prevent path traversal attacks.
Deploy the Sigma rule Detect Heym Path Traversal File Upload (CVE-2026-45225) to detect exploitation attempts in web server logs.
Monitor web server logs for HTTP requests to the file upload endpoint containing suspicious filename patterns.

Heym Sandbox Escape Vulnerability (CVE-2026-45227)

hello@craftedsignal.io — Tue, 12 May 2026 22:18:20 +0000

Heym before version 0.0.21 contains a critical sandbox escape vulnerability, identified as CVE-2026-45227, within its custom Python tool executor. This flaw enables authenticated workflow authors to circumvent intended sandbox restrictions by leveraging object-graph introspection primitives. By exploiting this vulnerability, attackers can regain access to the unrestricted __import__ function, enabling the import of typically blocked modules such as os and subprocess. This access further allows attackers to access inherited backend environment variables, potentially exposing sensitive information such as database credentials and encryption keys. Successful exploitation leads to arbitrary host command execution with the privileges of the backend service user, severely compromising system integrity.

Attack Chain

An authenticated user gains access to the Heym workflow authoring interface.
The attacker crafts a malicious workflow using the custom Python tool executor.
The workflow exploits Python introspection techniques to access the unrestricted __import__ function.
Using the recovered __import__ function, the attacker imports restricted modules like os or subprocess.
The attacker uses the imported modules to access inherited backend environment variables.
The attacker extracts sensitive data like database credentials or encryption keys from environment variables.
The attacker crafts an arbitrary OS command using the os or subprocess modules.
The malicious workflow executes the arbitrary OS command on the host, running as the backend service user.

Impact

Successful exploitation of this sandbox escape vulnerability (CVE-2026-45227) in Heym allows attackers to execute arbitrary commands on the host system as the backend service user. This can lead to complete system compromise, including data theft, service disruption, and unauthorized access to sensitive information, including database credentials and encryption keys. The vulnerability affects all Heym deployments prior to version 0.0.21.

Recommendation

Upgrade Heym to version 0.0.21 or later to patch CVE-2026-45227.
Deploy the Sigma rule “Detect Heym Sandbox Escape Attempt via Import” to monitor for attempts to import restricted modules within the Python tool executor.
Review and restrict access to the Heym workflow authoring interface to minimize the attack surface.

Heym Authorization Bypass Vulnerability CVE-2026-45226

hello@craftedsignal.io — Tue, 12 May 2026 22:18:07 +0000

Heym before version 0.0.21 is vulnerable to an authorization bypass, as identified by CVE-2026-45226. This flaw allows authenticated users to bypass access controls and execute arbitrary workflows. The vulnerability stems from a lack of proper access validation when referencing workflow UUIDs. Attackers can exploit this by creating malicious workflows that reference UUIDs of victim workflows, enabling them to load and execute these workflows under attacker-controlled execution paths. This leads to potential exposure of sensitive victim workflow outputs and unintended triggering of workflow nodes with adverse side effects. This vulnerability poses a significant risk to the confidentiality and integrity of workflows within Heym environments.

Attack Chain

An attacker authenticates to a Heym instance.
The attacker identifies a victim workflow and obtains its UUID.
The attacker creates a new workflow containing either an “execute” node or an “agent subWorkflowId”.
Within the “execute” node or “agent subWorkflowId”, the attacker references the victim workflow’s UUID.
The attacker executes their newly crafted workflow.
Due to the authorization bypass, the Heym system loads and executes the victim workflow under the attacker’s execution context.
The attacker gains access to the victim workflow’s outputs.
Workflow nodes within the victim workflow are triggered with unintended side effects, potentially causing further damage.

Impact

Successful exploitation of CVE-2026-45226 allows an attacker to execute arbitrary workflows without proper authorization. This can lead to the exposure of sensitive data contained within the victim workflows, as well as the unintended triggering of workflow nodes, potentially causing data corruption or other malicious side effects. The vulnerability affects Heym instances before version 0.0.21 and poses a risk to the confidentiality, integrity, and availability of workflow data.

Recommendation

Upgrade Heym to version 0.0.21 or later to patch CVE-2026-45226.
Deploy the Sigma rule “Detect Heym Workflow Execution with Subworkflow UUID” to identify potentially malicious workflow executions.
Monitor Heym logs for unauthorized workflow executions referencing unusual or suspicious workflow UUIDs.