CVE-2026-101049 in Heym
Summary
by MITRE • 09/27/2026
Heym before 0.0.53 fails to verify Slack request signatures when trigger nodes lack credential IDs or have empty signing secrets. Remote unauthenticated attackers can send forged Slack events to known webhook URLs to trigger workflows with the owner's credentials.
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Analysis
by VulDB Data Team • 09/27/2026
The Heym application, prior to version 0.0.53, contains a critical authentication bypass vulnerability stemming from improper verification of incoming webhooks originating from Slack. This flaw specifically affects the integration logic that processes events sent by Slack via HTTP POST requests. The core issue lies in the failure to validate cryptographic signatures when specific configuration conditions are met: namely, when trigger nodes within the workflow lack associated credential identifiers or possess empty signing secrets. In a properly secured implementation, every incoming webhook request must be signed using a shared secret known only to the application and Slack. Upon receipt of an event, Heym is required to compute a hash-based message authentication code (HMAC) using this secret and compare it against the signature provided in the request headers. If these values do not match exactly, the request should be rejected as unauthorized. However, due to the identified defect, if the signing secret field is empty or undefined during the validation process, Heym erroneously accepts the request without performing any cryptographic verification. This effectively disables the authentication mechanism for those specific workflow triggers, leaving them wide open to external manipulation.
This vulnerability allows remote unauthenticated attackers to forge Slack events and send them directly to known webhook URLs associated with vulnerable instances of Heym. By crafting malicious HTTP requests that mimic legitimate Slack event payloads, an attacker can trigger workflows configured in this manner without possessing valid credentials or authorization from the workflow owner. The operational impact is severe, as these forged triggers execute actions under the context of the account holder's permissions. Depending on the specific integrations connected to Heym, such unauthorized execution could lead to data exfiltration, modification of sensitive records, deletion of critical information, or further lateral movement within an organization’s infrastructure if downstream services are compromised. The attacker does not need prior access to the Slack workspace nor do they need to bypass any other security controls; they simply exploit the missing signature verification logic to inject arbitrary commands into the workflow engine.
From a classification perspective, this vulnerability aligns with CWE-287, which describes Improper Authentication, as the system fails to adequately verify the identity of the sender before granting access or executing privileged operations. It also relates closely to CWE-345, Insufficient Verification of Data Authenticity, because the application does not confirm that the data originated from a trusted source via cryptographic means. In terms of offensive security frameworks, this exploit scenario maps directly to MITRE ATT&CK technique T1078, Valid Accounts, specifically in the context of using legitimate credentials or configurations for unauthorized access through misconfiguration rather than credential theft. It also reflects aspects of T1564, Hidden Files and Directories, if attackers use these forged events to maintain persistence or evade detection by blending malicious activity with normal webhook traffic patterns.
To mitigate this vulnerability, organizations running Heym must immediately upgrade to version 0.0.53 or later, where the signature verification logic has been corrected to enforce strict validation regardless of configuration states. For environments that cannot update immediately due to operational constraints, a temporary workaround involves ensuring that all trigger nodes are explicitly configured with valid, non-empty signing secrets and corresponding credential IDs before accepting any external webhook traffic. Additionally, network-level controls such as IP allow-listing for Slack’s known server addresses can provide an additional layer of defense by restricting which sources can send requests to the Heym endpoints. Regular security audits should be conducted to identify other integrations that may suffer from similar misconfigurations where authentication checks are conditionally skipped based on empty or null values in configuration files.