CVE-2026-27771: Gitea Composer Package Source Information Disclosure Vulnerability

Technical summary

CVE-2026-27771 stems from insufficient authorization checks on Composer package source link endpoints in Gitea. The vulnerability is rooted in missing or inadequate permission validation (CWE-862) that fails to enforce access controls on package metadata. An attacker can make unauthenticated network requests to retrieve Composer package source information, including private repository URLs and credentials, that should be restricted to authorized users. The CVSS 3.0 score of 8.2 reflects high confidentiality impact with limited integrity risk and no availability impact.

Business impact

Exposure of private or internal package source information creates multiple business risks. Competitors or malicious actors could discover internal dependency chains, proprietary package repositories, or third-party integrations. In worst-case scenarios, embedded authentication tokens or API keys in package source URLs could be harvested and used to compromise downstream systems. Organizations relying on Gitea for supply chain security are at risk of elevated OSINT attacks targeting their development infrastructure. Remediation delay extends the window during which information disclosure can occur.

Affected systems

Gitea versions up to and including 1.26.1 are vulnerable. Organizations using self-hosted Gitea instances with Composer package management enabled are directly affected. The vulnerability requires no special configuration; any Gitea installation with Composer packages stored or proxied is potentially exposed if running a vulnerable version. Hosted Gitea services and users on versions 1.26.2 or later are not affected.

Exploitability

This vulnerability is highly exploitable. It requires no authentication, no user interaction, and can be triggered over the network from any internet-connected attacker. The attack surface is straightforward: crafted HTTP requests to package endpoints can leak sensitive metadata. No special tooling is required beyond a standard HTTP client. The low attack complexity and network-based vector make this a concern for organizations with internet-exposed Gitea instances.

Remediation

Upgrade Gitea to a patched version that includes authorization checks for Composer package source endpoints. Verify the exact version requirements against the official Gitea security advisory. If immediate patching is not possible, consider network segmentation to restrict unauthenticated access to Gitea instances, implement WAF rules to block suspicious package metadata queries, and audit logs for signs of information disclosure attempts. Review any exposed package source credentials and rotate authentication tokens as a precaution.

Patch guidance

Consult the official Gitea security advisory and release notes for the specific patched version addressing CWE-862 authorization gaps in Composer package handling. Apply the patch during a planned maintenance window and validate that Composer package source links are no longer accessible without proper authentication. Test both public and private package repositories post-patch to confirm access controls are enforced.

Detection guidance

Monitor Gitea access logs for unauthenticated requests to Composer package source endpoints (typically paths like `/api/packages/composer/*` or similar). Alert on repeated or systematic queries from a single source attempting to enumerate package metadata. Implement intrusion detection rules to flag requests lacking valid authentication tokens accessing package information. Review historical logs from the disclosure date (July 3, 2026) onward to identify potential reconnaissance activity.

Why prioritize this

This vulnerability merits immediate priority due to its high CVSS score (8.2), unauthenticated attack vector, and direct exposure of sensitive supply chain information. Unlike many vulnerabilities requiring privileged access or user interaction, this one is trivial to exploit and places intellectual property and infrastructure credentials at risk. Organizations with internet-facing Gitea instances should treat this as urgent.

Risk score, explained

The CVSS 3.0 score of 8.2 (HIGH) reflects a network-based, unauthenticated attack that causes high confidentiality impact through information disclosure of package sources and embedded credentials. The limited integrity impact acknowledges that the attacker cannot modify data; however, the exposure of metadata and secrets justifies the high severity. The absence of availability impact prevents a critical rating.

Frequently asked questions