CVE-2026-25229: Gogs Auth Bypass Vulnerability

CVE-2026-25229 Overview

CVE-2026-25229 is a Broken Access Control vulnerability affecting Gogs, the popular open-source self-hosted Git service. This security flaw allows authenticated users with write access to any repository to modify labels belonging to other repositories, leading to potential cross-repository label tampering attacks.

The vulnerability exists in the Web UI's label update endpoint POST /:username/:reponame/labels/edit. The handler function UpdateLabel in internal/route/repo/issue.go uses an incorrect database query function that bypasses repository ownership validation, enabling attackers to manipulate labels across repository boundaries.

Critical Impact

Authenticated attackers can modify labels belonging to repositories they do not own, potentially disrupting issue tracking workflows and enabling social engineering attacks through label manipulation.

Affected Products

• Gogs versions 0.13.4 and below

Discovery Timeline

• 2026-02-19 - CVE CVE-2026-25229 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-25229

Vulnerability Analysis

This vulnerability represents a classic Broken Access Control (CWE-284) flaw where authorization checks fail to validate resource ownership. The UpdateLabel function processes label modification requests without verifying that the target label belongs to the repository specified in the URL path.

When a user sends a POST request to the label edit endpoint, the application extracts the label ID from the request body but fails to cross-reference it against the repository context from the URL. This architectural weakness means an attacker can manipulate labels in repositories where they have no write permissions, as long as they have authenticated access to at least one repository with write permissions.

The attack is network-accessible and requires low privilege (authenticated user with write access to any repository). No user interaction is required for exploitation, making this a straightforward attack vector for malicious insiders or compromised accounts.

Root Cause

The root cause lies in the UpdateLabel function within internal/route/repo/issue.go. The function uses a database query that retrieves labels by ID without filtering by the current repository context. This means any valid label ID can be modified regardless of which repository it belongs to.

The correct implementation should validate that the label's repository ID matches the repository ID from the current URL context before allowing any modifications. The fix in version 0.14.1 addresses this by adding proper repository ownership validation to the database query.

Attack Vector

The attack leverages the network-accessible Web UI endpoint. An authenticated attacker with write access to any repository on the Gogs instance can craft malicious POST requests to the label edit endpoint, specifying label IDs from other repositories they do not control.

The attack flow involves: (1) authenticating to the Gogs instance with a valid account that has write access to at least one repository, (2) enumerating or guessing label IDs from target repositories, and (3) sending crafted POST requests to modify those labels. Since label IDs are typically sequential integers, enumeration is trivial.

The vulnerability mechanism involves the missing repository ownership check in the label update handler. The endpoint accepts a label ID in the request body but only validates that the user has write access to the repository in the URL path, not that the label actually belongs to that repository. For full technical details, see the GitHub Security Advisory.

Detection Methods for CVE-2026-25229

Indicators of Compromise

• Unexpected modifications to repository labels not initiated by repository administrators
• Audit log entries showing label modifications where the target label's repository differs from the user's primary repository
• Patterns of label ID enumeration in web server access logs targeting the /labels/edit endpoint
• User complaints about labels being renamed, recolored, or deleted without authorization

Detection Strategies

• Monitor web server access logs for POST requests to /:username/:reponame/labels/edit endpoints with unusual patterns or high frequency
• Implement application-level logging to capture label modification events with full context including user, source repository, and target label details
• Deploy Web Application Firewall (WAF) rules to detect parameter manipulation attempts in label edit requests
• Enable database audit logging to track label table modifications and correlate with HTTP request logs

Monitoring Recommendations

• Configure alerting for label modifications occurring outside normal business hours or from unusual IP addresses
• Establish baseline metrics for label modification frequency and alert on statistical anomalies
• Review Gogs application logs regularly for error messages related to authorization failures that may indicate exploitation attempts
• Implement real-time monitoring of the /labels/edit endpoint response times and error rates

How to Mitigate CVE-2026-25229

Immediate Actions Required

• Upgrade Gogs to version 0.14.1 or later immediately
• Audit existing labels across all repositories to identify any unauthorized modifications
• Review access logs for suspicious label modification activity prior to patching
• Consider temporarily restricting label editing capabilities through reverse proxy rules until patching is complete

Patch Information

The vulnerability has been fixed in Gogs version 0.14.1. The patch modifies the UpdateLabel function to properly validate that the label being modified belongs to the repository specified in the URL path before processing any changes. The fix can be reviewed in the GitHub commit.

Organizations should upgrade to version 0.14.1 or later by following the standard Gogs upgrade procedure. Backup your Gogs installation before upgrading, and verify label integrity after the upgrade is complete.

Workarounds

• Implement reverse proxy rules to restrict access to the /labels/edit endpoint to only trusted administrator IP addresses
• Reduce the attack surface by limiting write access to repositories on a need-to-have basis
• Deploy a Web Application Firewall with custom rules to validate that label operations only target labels within the authenticated user's authorized repositories
• Consider running Gogs in a more isolated network segment with strict access controls until patching can be completed

# Example nginx configuration to restrict label editing endpoint
location ~ ^/[^/]+/[^/]+/labels/edit$ {
    # Allow only trusted admin IPs until Gogs is patched
    allow 192.168.1.100;
    allow 10.0.0.50;
    deny all;
    
    proxy_pass http://gogs_backend;
}