Denial of Service via String Concatenation in Debian Package Upload

Executive Summary

CVE-2026-56755 is a Denial of Service vulnerability in Gitea versions up to 1.26.4. It involves two issues in the Debian package registry parser: unbounded decompression in the ParseControlFile function and O(N²) string concatenation in the Description field processing. Attackers can exploit these by uploading a specially crafted .deb file to exhaust server memory and CPU resources.

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Detection Guidance

To detect this vulnerability, monitor for unusually high CPU or memory usage during Debian package uploads or registry operations. Check Gitea logs for failed uploads or timeouts. Inspect network traffic for large .deb files being processed. Ensure Gitea version is updated to 1.27.0 or later.

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Impact Analysis

If you use Gitea versions up to 1.26.4, an authenticated user with write access to the package registry could upload a malicious .deb file. This would cause CPU and memory exhaustion, leading to service disruption, slowdowns, or crashes. The attack requires only a single upload request.

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Compliance Impact

This vulnerability could lead to service unavailability, which may violate availability requirements in GDPR and HIPAA. Downtime could result in unauthorized access to data or failure to meet data processing timelines, potentially leading to compliance breaches.

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Mitigation Strategies

Immediately upgrade Gitea to version 1.27.0 or later to patch the vulnerability. Restrict write access to the package registry to trusted users only. Monitor server resources for signs of exploitation. Consider disabling the Debian package registry if not in use.

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