CVE-2026-103667 in Gitea
Summary
by MITRE • 10/06/2026
Gitea's container registry served blob downloads with a `Content-Type` taken from the media type declared in pushed image manifests, without a `Content-Disposition` or restrictive content security policy. A user who can push container images can publish a blob containing HTML and JavaScript with a `text/html` media type. When a victim who is authenticated to the instance opens the blob URL in a browser, the script runs on the Gitea origin and can perform actions as the victim, such as creating API tokens.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified in Gitea's container registry stems from an improper neutralization of special elements within HTTP response headers, specifically regarding how content types are handled during blob retrieval operations. When a user pushes a container image to the registry, the system extracts the media type declared in the manifest and applies it directly as the Content-Type header for subsequent downloads of that specific blob layer. This design choice fails to enforce strict validation or sanitization of the declared MIME type against expected formats for binary data typically stored in registries, such as application/octet-stream or image layers. Consequently, if a malicious actor pushes an artifact with a manifest declaring text/html as its media type, the server will serve that content with the corresponding Content-Type header, signaling to web browsers and other HTTP clients that the payload is executable HTML rather than opaque binary data.
This misconfiguration creates a significant cross-site scripting risk because modern web browsers rely heavily on the Content-Type header to determine how to parse incoming responses. By serving maliciously crafted blobs as text/html without additional safeguards like restrictive Content Security Policy headers or explicit Content-Disposition directives that force file downloads, Gitea allows these payloads to be executed directly within the context of the authenticated user's session. The absence of a Content-Disposition header means the browser does not treat the response as an attachment requiring download but instead renders it inline in the current window. This behavior effectively bypasses standard security expectations for container registries, which are generally assumed to store static binary artifacts rather than interactive web content.
The operational impact of this vulnerability is severe due to its potential for account takeover and privilege escalation within the Gitea instance. An authenticated victim who navigates to or loads a URL pointing to such a maliciously crafted blob will have their browser execute the embedded JavaScript code on the origin domain of the Gitea server. Because the script runs with the full privileges of the logged-in user, an attacker can leverage this execution context to perform arbitrary actions on behalf of the victim. This includes but is not limited to creating new API tokens, which could grant long-term access to repositories and services, modifying repository settings, or exfiltrating sensitive data stored within the platform's scope. The attack vector requires only that the victim be authenticated and visit a specific URL constructed by the attacker, making it feasible for phishing campaigns targeting Gitea administrators or developers with elevated permissions.
From a classification perspective, this issue aligns closely with CWE-79, which describes improper neutralization of input during web page generation known as cross-site scripting. The root cause is categorized under CWE-693, where the protection mechanism fails to prevent an attacker from using protected resources against their intended policy. In terms of tactical mapping within the MITRE ATT&CK framework, this vulnerability facilitates initial access and credential access techniques by allowing attackers to hijack active sessions through browser-based execution contexts. The lack of restrictive content security policies further exacerbates the risk by removing a critical layer of defense that could otherwise limit script execution origins or restrict API interactions initiated from untrusted sources.
To mitigate this vulnerability, Gitea administrators should ensure they are running a patched version of the software where the container registry logic has been updated to enforce stricter MIME type validation. The system must be configured to serve all blob downloads with a neutral content type such as application/octet-stream or image/vnd.zstd-compressed-tar regardless of what is declared in the manifest, thereby preventing browsers from interpreting binary data as executable code. Additionally, implementing robust Content Security Policy headers that restrict script execution and API calls can provide defense-in-depth against similar exploitation attempts. It is also recommended to audit existing container images for any potentially malicious manifests and rotate any API tokens or credentials if there is suspicion of prior exposure through this vector.