CVE-2026-20800: Gitea Information Disclosure Vulnerability

CVE-2026-20800 Overview

CVE-2026-20800 is an information disclosure vulnerability in Gitea's notification API that fails to re-validate repository access permissions when returning notification details. This security flaw allows users whose access to a private repository has been revoked to continue viewing issue and pull request titles through previously received notifications, potentially exposing sensitive project information.

Critical Impact

Users with revoked repository access can continue to view private issue and pull request titles through cached notifications, potentially leaking sensitive project information and internal development details.

Affected Products

• Gitea versions prior to 1.25.4

Discovery Timeline

• 2026-01-22 - CVE CVE-2026-20800 published to NVD
• 2026-01-22 - Last updated in NVD database

Technical Details for CVE-2026-20800

Vulnerability Analysis

This vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The core issue lies in Gitea's notification API implementation, which caches notification data without performing subsequent access control validation when serving that data to users.

When a user receives notifications about issues or pull requests in a private repository, those notification details are stored and associated with the user's account. The vulnerability occurs because when the notification API is queried, it returns these cached notification details without checking whether the user currently has valid access to the associated repository.

This creates a window where access control decisions made at the repository level are not propagated to the notification subsystem, allowing information to leak to users who should no longer have visibility into the repository's contents.

Root Cause

The root cause is insufficient access control validation in the notification API endpoint. The API trusts that notifications stored for a user are always valid to display, without considering that the user's access permissions may have changed since the notification was generated. This represents a failure to implement proper access control checks at the point of data retrieval, violating the principle of checking authorization for every access request.

Attack Vector

An attacker who previously had legitimate access to a private repository could exploit this vulnerability through the following mechanism:

1. The attacker gains authorized access to a private repository (as a collaborator, team member, or organization member)
2. While having access, the attacker receives notifications about issues and pull requests in the repository
3. The attacker's access to the repository is subsequently revoked by an administrator
4. After revocation, the attacker queries the Gitea notification API
5. The API returns notification details including issue and pull request titles from the private repository
6. The attacker can view sensitive information they should no longer have access to

This vulnerability requires no special technical skills to exploit once a user's access has been revoked—simply accessing the notification endpoint through normal API calls or the web interface is sufficient.

Detection Methods for CVE-2026-20800

Indicators of Compromise

• Unusual notification API access patterns from users who have had repository access recently revoked
• API requests to notification endpoints from user accounts that no longer have any active repository memberships
• Correlation of access revocation events with subsequent notification API queries from the same users

Detection Strategies

• Implement logging for notification API access and correlate with repository access changes
• Monitor for users accessing notification data after their repository permissions have been modified
• Review audit logs for notification endpoint queries from users with no current repository access
• Implement alerting on notification API access patterns that occur shortly after access revocation events

Monitoring Recommendations

• Enable detailed API access logging for the notification endpoints
• Create dashboards tracking the relationship between permission changes and notification access
• Configure alerts for notification API access by users with recently revoked permissions
• Periodically audit notification data retention policies and access patterns

How to Mitigate CVE-2026-20800

Immediate Actions Required

• Upgrade Gitea to version 1.25.4 or later immediately
• Review recent repository access revocations and assess potential information exposure
• Audit notification data for sensitive information that may have been exposed
• Consider implementing additional access controls at the network or application gateway level

Patch Information

Gitea has released version 1.25.4 which addresses this vulnerability. The fix ensures that the notification API re-validates repository access permissions before returning notification details to users. For detailed information about the fix implementation, refer to the Gitea Pull Request #36339 and the Gitea Release Announcement.

The official security advisory is available at the GitHub Security Advisory GHSA-g54m-9f6g-wj7q.

Workarounds

• If immediate patching is not possible, consider restricting access to the notification API endpoints at the reverse proxy or firewall level
• Implement manual notification cleanup procedures when revoking user access to sensitive repositories
• Review and limit what information is included in notification titles for private repositories
• Consider temporarily disabling notification features for highly sensitive repositories until the patch can be applied

# Upgrade Gitea to patched version
# Stop Gitea service
sudo systemctl stop gitea

# Download and install Gitea 1.25.4
wget https://github.com/go-gitea/gitea/releases/download/v1.25.4/gitea-1.25.4-linux-amd64
chmod +x gitea-1.25.4-linux-amd64
sudo mv gitea-1.25.4-linux-amd64 /usr/local/bin/gitea

# Restart Gitea service
sudo systemctl start gitea

# Verify version
gitea --version