CVE-2026-27657: Gitea Auth Bypass Vulnerability

CVE-2026-27657 Overview

CVE-2026-27657 is an authorization flaw in Gitea versions before 1.25.5. The vulnerability allows an authenticated user to change another user's primary email address without proper authorization checks. This weakness maps to [CWE-639]: Authorization Bypass Through User-Controlled Key. Successful exploitation compromises account integrity and enables downstream attacks such as password reset hijacking and identity impersonation within the Git hosting platform. The issue is fixed in Gitea 1.25.5, released with associated pull requests #36586 and #36607.

Critical Impact
An authenticated attacker can modify the primary email address of any other Gitea user, enabling account takeover through password reset workflows.

Affected Products

Gitea versions prior to 1.25.5
Self-hosted Gitea Git service instances
Any deployment relying on Gitea email-based account recovery

Discovery Timeline

2026-07-03 - CVE-2026-27657 published to NVD
2026-07-07 - Last updated in NVD database

Technical Details for CVE-2026-27657

Vulnerability Analysis

Gitea is an open-source, self-hosted Git service written in Go. The vulnerability resides in the account management logic responsible for modifying user email records. Prior to version 1.25.5, the endpoint that handles primary email changes did not correctly validate that the target email record belonged to the requesting user. An authenticated user can therefore issue a request that alters another account's primary email address.

Because the primary email governs account notifications and password reset delivery, changing it effectively redirects recovery flows to an attacker-controlled address. The classification [CWE-639] applies because the flaw stems from trusting a user-supplied identifier without enforcing that it maps to the requester's own account.

Root Cause

The root cause is missing ownership validation on the email modification handler. The code path accepts an email or user reference from the request and updates the associated record without confirming that the authenticated principal owns it. Fixes in pull requests #36586 and #36607 add the required authorization checks before mutating email records.

Attack Vector

The attack is executed over the network by any authenticated Gitea user. The attacker submits a crafted request to the email management endpoint that references another user's email or account identifier. Once the primary email is replaced, the attacker triggers a password reset. Gitea sends the reset link to the newly assigned attacker-controlled address, enabling full account takeover including access to private repositories, secrets, and CI/CD integrations.

No verified public proof-of-concept code is available at the time of publication. See the Gitea Blog Release Announcement and the linked pull requests for technical details of the fix.

Detection Methods for CVE-2026-27657

Indicators of Compromise

Unexpected changes to the primary_email field on user accounts in the Gitea database.
Password reset requests followed by primary email changes for the same account within a short window.
Authentication events from new IP addresses or user agents shortly after an email change.
Outbound email delivery logs showing password reset emails sent to previously unknown addresses.

Detection Strategies

Audit the Gitea email_address table for records where is_primary = true and updated_unix occurred before applying the 1.25.5 patch.
Correlate Gitea application logs for POST and PATCH requests to /user/settings/email and API email endpoints against the authenticated session's user ID.
Alert when the acting user ID in a request does not match the owning user ID of the modified email record.

Monitoring Recommendations

Forward Gitea application and access logs to a centralized log platform and retain them for at least 90 days.
Monitor administrative and account-settings endpoints for anomalous request rates or cross-account references.
Enable and review Gitea's built-in audit logging for account and email modification events.

How to Mitigate CVE-2026-27657

Immediate Actions Required

Upgrade Gitea to version 1.25.5 or later without delay.
Review recent email change events and reset credentials for any account with an unexplained primary email modification.
Rotate personal access tokens, OAuth application secrets, and SSH keys for potentially affected accounts.
Notify users of the incident and require re-verification of their primary email address post-upgrade.

Patch Information

The Gitea maintainers addressed CVE-2026-27657 in release v1.25.5. The corrective changes are tracked in pull requests #36586 and #36607, which enforce ownership validation on email management operations. Refer to the Gitea Blog Release Announcement for the full changelog.

Workarounds

Restrict Gitea instance access to trusted, authenticated users using network-level controls until the upgrade is complete.
Temporarily disable self-service email modification through reverse-proxy rules if upgrading immediately is not feasible.
Enforce mandatory two-factor authentication so that account takeover via password reset requires an additional factor.

bash

# Upgrade Gitea to the patched release (binary deployment example)
systemctl stop gitea
wget https://github.com/go-gitea/gitea/releases/download/v1.25.5/gitea-1.25.5-linux-amd64 -O /usr/local/bin/gitea
chmod +x /usr/local/bin/gitea
systemctl start gitea
gitea --version