CVE-2026-27780 in Gitea
Summary
by MITRE • 07/04/2026
Gitea versions before 1.26.0 do not fail closed on bufio.Scanner errors while processing pre-receive hook input, allowing oversized input to bypass branch-protection checks.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/04/2026
Gitea is a self-hosted Git service that provides repository management, issue tracking, and continuous integration capabilities for development teams. The vulnerability affects versions prior to 1.26.0 where the pre-receive hook processing mechanism fails to properly handle bufio.Scanner errors during input validation. This flaw occurs when the system processes incoming git operations through pre-receive hooks that enforce branch protection rules. The failure to close the process properly on scanner errors creates a condition where malformed or oversized input can bypass critical security controls designed to prevent unauthorized changes to protected branches.
The technical implementation involves the bufio.Scanner component which reads input from stdin during pre-receive hook execution. When the scanner encounters input that exceeds buffer limits or causes parsing errors, the system should terminate the operation and reject the input. However, in affected versions, the error handling mechanism fails to properly close the process flow, allowing oversized payloads to continue processing beyond the initial validation stage. This creates a scenario where branch protection mechanisms are circumvented because the system never properly validates the full scope of incoming changes.
The operational impact of this vulnerability is significant for organizations relying on Gitea for source code management and collaboration. Attackers can exploit this weakness by crafting oversized inputs that trigger scanner errors, thereby bypassing branch protection rules that normally prevent direct pushes to protected branches such as main or develop. This could enable malicious actors to push unauthorized changes directly to critical development branches without proper review or approval processes. The vulnerability essentially undermines the core security controls designed to maintain code integrity and prevent accidental or intentional disruptions to important repository states.
This vulnerability can be classified under CWE-248, which addresses "Uncaught Exception" conditions in software implementations. It also maps to ATT&CK technique T1078.004 for "Valid Accounts: Cloud Infrastructure and Services" where an attacker might leverage this bypass to gain unauthorized access to protected code repositories. The failure to properly handle scanner errors creates a path for privilege escalation through repository access controls, potentially allowing attackers to modify critical source code without proper authorization.
Organizations should immediately update to Gitea version 1.26.0 or later where the pre-receive hook error handling has been corrected to properly close processes on bufio.Scanner failures. Administrators should also review existing branch protection rules and consider implementing additional monitoring for unusual push patterns that might indicate exploitation attempts. The fix ensures that when scanner errors occur during input processing, the system terminates the operation completely rather than allowing oversized inputs to proceed through validation checks. Security teams should monitor repository access logs for any anomalous activity that might indicate attempted exploitation of this vulnerability before the patch was applied.