CVE-2025-61926: Allstar Reviewbot has Authentication Bypass via Hard-coded Webhook Secret
A vulnerability in Allstar’s Reviewbot component caused inbound webhook requests to be validated against a hard-coded, shared secret:
https://github.com/ossf/allstar/blob/294ae985cc2facd0918e8d820e4196021aa0b914/pkg/reviewbot/reviewbot.go#L59
The value used for the secret token was compiled into the Allstar binary and could not be configured at runtime. In practice, this meant that every deployment using Reviewbot would validate requests with the same secret unless the operator modified source code and rebuilt the component - an expectation that is not documented and is easy to miss. While Reviewbot is not commonly enabled in standard Allstar setups, we are issuing this advisory to reach any environments where it may have been deployed.
Affected Versions
All Allstar releases prior to v4.5 that include the Reviewbot code path are affected. Deployments on v4.5 and later are not affected. If you have not enabled or exposed the Reviewbot endpoint, this issue does not apply to your installation.
Impact
If the Reviewbot endpoint is deployed and reachable, an attacker can bypass authentication by crafting webhook requests that use the known, hard-coded secret. Because signature verification will succeed, Reviewbot would treat these requests as authentic when they should be rejected. Depending on the permissions and automations attached to your deployment, this could allow unauthorized triggering of review actions such as posting automated comments or reviews, influencing checks, or otherwise manipulating repository signals. The primary risk is to the integrity of repository workflows rather than confidentiality or availability, although secondary effects (e.g., noisy automation, misleading reviews, or workflow disruptions) are possible.
Exploitability
Exploiting this is straightforward and does not require an attacker to be authenticated. Anyone who can send requests to the Reviewbot webhook can reach the vulnerable code.
Other sources
Allstar is a GitHub App to set and enforce security policies. In versions prior to 4.5, a vulnerability in Allstar’s Reviewbot component caused inbound webhook requests to be validated against a hard-coded, shared secret. The value used for the secret token was compiled into the Allstar binary and could not be configured at runtime. In practice, this meant that every deployment using Reviewbot would validate requests with the same secret unless the operator modified source code and rebuilt the component - an expectation that is not documented and is easy to miss. All Allstar releases prior to v4.5 that include the Reviewbot code path are affected. Deployments on v4.5 and later are not affected. Those who have not enabled or exposed the Reviewbot endpoint are not exposed to this issue.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/ossf/allstarto a version that resolves this vulnerability.Fixed in 0.0.0-20250721181116-e004ecb540d6 - Upgrade
Upgrade
Allstarto a version that resolves this vulnerability.Fixed in v4.5
Event History
Frequently Asked Questions
What is the severity of CVE-2025-61926?
CVE-2025-61926 has been classified as a high-severity vulnerability due to its potential impact on the security of the GitHub Allstar application.
How do I fix CVE-2025-61926?
To fix CVE-2025-61926, upgrade your GitHub Allstar application to version 4.5 or later.
What types of systems are affected by CVE-2025-61926?
CVE-2025-61926 affects all installations of GitHub Allstar prior to version 4.5.
What does CVE-2025-61926 exploit?
CVE-2025-61926 exploits a vulnerability in the Reviewbot component related to hard-coded shared secrets used for validating webhook requests.
What are the consequences of CVE-2025-61926?
The consequences of CVE-2025-61926 can include unauthorized access to sensitive information through manipulated webhook requests.