The vulnerability identified as CVE-2025-61926 affects the ossf allstar GitHub App, a tool designed to enforce security policies on GitHub repositories. In versions prior to 4.5, the Reviewbot component uses a hard-coded secret token to validate inbound webhook requests. This secret is embedded directly into the compiled binary and cannot be changed at runtime, leading to a scenario where every deployment shares the same secret unless the operator modifies the source code and rebuilds the component—a process that is neither documented nor commonly performed. This insecure default variable initialization (CWE-453) and use of a hard-coded secret (CWE-798) allow an attacker to craft malicious webhook requests that pass validation checks, potentially enabling unauthorized actions or bypassing security policies enforced by Allstar. The vulnerability is remotely exploitable without authentication or user interaction, increasing its risk profile. However, it only affects deployments that have enabled and exposed the Reviewbot endpoint. The vulnerability has a CVSS 4.6 (medium) score, reflecting moderate impact primarily on integrity. The issue was addressed in version 4.5 by removing the hard-coded secret and allowing proper configuration. No public exploits have been reported to date.

For European organizations, this vulnerability could undermine the integrity of security policy enforcement on GitHub repositories managed via Allstar, potentially allowing attackers to bypass or manipulate security controls. This could lead to unauthorized code changes, policy violations, or exposure of sensitive development workflows. Organizations relying on Allstar’s Reviewbot to automate security governance are at risk if they use affected versions with exposed endpoints. The impact is particularly relevant for organizations with critical software supply chains or those under regulatory scrutiny for secure development practices. While the vulnerability does not directly affect confidentiality or availability, the integrity compromise could facilitate further attacks or compliance failures. Since exploitation requires no authentication and can be performed remotely, the threat is accessible to a wide range of attackers. However, the absence of known exploits and the medium severity score suggest the risk is moderate but should not be ignored, especially in environments where Allstar is integral to security policy enforcement.

European organizations should immediately verify if they are running ossf allstar versions prior to 4.5 with the Reviewbot component enabled and exposed. The primary mitigation is to upgrade all deployments to version 4.5 or later, where the hard-coded secret has been removed and replaced with configurable secrets. If upgrading is not immediately feasible, organizations should restrict network access to the Reviewbot endpoint, limiting it to trusted sources only, to reduce exposure. Additionally, operators should audit their deployments to ensure that the Reviewbot endpoint is not unnecessarily enabled or exposed. Reviewing webhook logs for unusual or unauthorized requests can help detect attempted exploitation. Organizations should also implement monitoring and alerting on anomalous webhook activity. Finally, documenting and enforcing secure deployment practices, including avoiding hard-coded secrets and ensuring proper configuration, will help prevent similar issues in the future.