CVE-2025-54575 is a medium severity vulnerability affecting the SixLabors ImageSharp 2D graphics library, specifically its GIF image decoder. The flaw exists in versions prior to 2.1.11 and between 3.0.0 and 3.1.10 inclusive. The vulnerability arises from improper handling of a malformed GIF comment extension block that lacks a proper block terminator. When processing such a crafted GIF file, the ImageSharp GIF decoder enters an infinite loop while attempting to skip the malformed comment block. This uncontrolled resource consumption leads to a denial of service (DoS) condition, as the application becomes unresponsive or consumes excessive CPU resources. The vulnerability does not impact confidentiality or integrity but affects availability. Exploitation requires no privileges or user interaction and can be triggered remotely by supplying a malicious GIF image to an application that uses a vulnerable ImageSharp version to process untrusted GIF inputs. The issue is addressed in ImageSharp versions 2.1.11 and 3.1.11, which properly handle the malformed comment extension block to avoid infinite looping. No known exploits are currently reported in the wild, but the vulnerability's nature makes it a potential vector for DoS attacks against services that accept GIF uploads or process GIF images from untrusted sources.

For European organizations, the primary impact of this vulnerability is service disruption due to denial of service attacks. Applications that rely on ImageSharp for image processing—such as web applications, content management systems, or digital asset management platforms—may become unresponsive or crash when processing malicious GIF files. This can degrade user experience, cause downtime, and potentially impact business operations, especially for organizations that handle large volumes of user-generated content or media files. While the vulnerability does not lead to data leakage or code execution, the availability impact can be significant in high-traffic environments or critical services. Additionally, attackers could exploit this vulnerability to conduct targeted DoS attacks against specific organizations or services, potentially as part of larger campaigns. The lack of required authentication or user interaction increases the risk, as attackers can remotely trigger the vulnerability by submitting crafted GIF files. European organizations with public-facing applications that accept image uploads are particularly at risk.

European organizations should immediately identify any applications or services using vulnerable versions of the SixLabors ImageSharp library (versions below 2.1.11 and between 3.0.0 and 3.1.10). The primary mitigation is to upgrade to the patched versions 2.1.11 or 3.1.11. In addition to patching, organizations should implement strict input validation and filtering on image uploads, including rejecting or sandboxing GIF files with suspicious or malformed metadata. Employing rate limiting and anomaly detection on image processing endpoints can help detect and mitigate potential DoS attempts. Where possible, isolate image processing workloads in separate containers or microservices with resource limits to prevent a single malicious input from affecting the entire application. Logging and monitoring for unusual CPU spikes or processing delays related to GIF handling should be established to enable rapid detection of exploitation attempts. Finally, organizations should review their incident response plans to include scenarios involving denial of service caused by malformed media files.