CVE-2026-27657: Gitea Email Change Vulnerability – Exploit, Patch & Detection

Technical summary

The vulnerability stems from inadequate authorization checks in Gitea's email management functionality (CWE-639: Authorization through User-Controlled Key). An attacker can send a crafted request over the network without authentication to modify another user's primary email address. The flaw exists because the application fails to properly verify that the requester has permission to change email settings for an account other than their own. This is exacerbated by the network-accessible nature of the endpoint and the lack of authentication requirements.

Business impact

Compromised email addresses on user accounts create multiple attack vectors. Attackers can leverage changed email addresses to reset forgotten passwords, intercept account recovery tokens, bypass email-based two-factor authentication flows, and redirect sensitive notifications away from legitimate users. For organizations running Gitea, this translates to potential unauthorized access to repositories, code theft, injection of malicious commits, and supply chain risks if Gitea is used for internal or open-source project management.

Affected systems

All Gitea installations running versions earlier than 1.25.5 are affected. This includes Gitea deployments on-premises, in containerized environments, and cloud-hosted instances. The vulnerability does not depend on specific configuration settings; it affects default installations. Organizations using Gitea for internal repositories, open-source project hosting, or as part of their CI/CD pipeline are at risk.

Exploitability

This vulnerability is highly exploitable. It requires no authentication, no user interaction, and can be triggered over the network with a simple HTTP request. An attacker with network access to a Gitea instance can immediately change the email of any user account. The low complexity of exploitation and absence of authentication barriers make this a practical attack vector in the wild. The CVSS score of 7.5 (HIGH) reflects the ease of exploitation and significant integrity impact, though confidentiality and availability are not directly affected.

Remediation

Organizations must upgrade to Gitea version 1.25.5 or later. This is a mandatory update with no workarounds. Before patching, consider temporary mitigations such as restricting network access to the Gitea instance via firewall rules or IP whitelisting, disabling public registration if not required, and monitoring for suspicious email change requests in audit logs. However, these are stopgap measures only; patching is the only complete remediation.

Patch guidance

Upgrade Gitea to version 1.25.5 or later. Consult your deployment method: for binary installations, download the latest release from the official Gitea repository; for Docker deployments, pull the 1.25.5 or newer image tag; for package managers, update through your distribution's package tool. Test the upgrade in a non-production environment first. The upgrade process is typically straightforward and does not require data migration for this fix.

Detection guidance

Monitor Gitea's audit logs and HTTP access logs for suspicious email modification requests, particularly those targeting multiple user accounts or originating from external IPs. Look for POST or PUT requests to user email endpoints executed by anonymous or low-privilege sessions. Email notification logs may reveal unexpected email change events. Network detection rules should flag repeated failed or successful email change attempts. Check for any user reports of unexpected email address changes on their accounts.

Why prioritize this

This vulnerability should be prioritized for immediate patching. It requires no authentication and has high exploitability, making it a prime target for automated attacks and credential compromise campaigns. The ease of exploitation combined with the direct path to account takeover elevates risk significantly. Organizations should treat this as critical in their patch management queue, even though it does not appear on CISA's KEV catalog at this time.

Risk score, explained

The CVSS 3.1 score of 7.5 reflects a HIGH severity vulnerability with critical business implications. The vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N breaks down as: network-accessible attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality impact (C:N), high integrity impact (I:H), and no availability impact (A:N). The integrity impact is high because email addresses are core identity attributes; compromise enables account takeover. The score appropriately reflects the practical severity despite not triggering confidentiality or availability directly.

Frequently asked questions