CVE-2025-11266 is an out-of-bounds write vulnerability classified under CWE-787 found in the Grassroots DICOM (GDCM) library, a widely used open-source toolkit for handling DICOM medical imaging files. The flaw is triggered during the parsing of DICOM files containing encapsulated PixelData fragments, which represent compressed image data stored as multiple fragments. Specifically, the vulnerability results from an unsigned integer underflow in buffer indexing logic when processing these fragments, causing an out-of-bounds memory write. This memory corruption leads to a segmentation fault, crashing the application and resulting in a denial-of-service (DoS) condition. Exploitation requires only that a user or system component opens a specially crafted malicious DICOM file, with no authentication or elevated privileges needed, and minimal user interaction (opening the file). The CVSS 4.0 score is 6.8 (medium severity), reflecting the local attack vector (file input), low complexity, no privileges required, but requiring user interaction. The vulnerability impacts confidentiality and integrity minimally but has a high impact on availability due to service crashes. No patches are currently linked, and no known exploits have been reported in the wild. Given the critical role of DICOM files in medical imaging workflows, this vulnerability poses a risk to healthcare environments relying on GDCM for image processing and viewing.

For European organizations, particularly healthcare providers and medical imaging centers, this vulnerability can cause significant disruption. The denial-of-service condition may interrupt diagnostic workflows, delay patient care, and reduce availability of imaging services. While it does not allow remote code execution or data exfiltration, the loss of availability in critical medical systems can have severe operational and patient safety consequences. Hospitals and clinics using software that integrates GDCM for DICOM parsing are at risk if they process untrusted or externally sourced DICOM files. Additionally, healthcare research institutions and medical device manufacturers in Europe that utilize GDCM could face service interruptions. The impact is heightened in countries with advanced healthcare infrastructure and widespread use of open-source DICOM libraries. Disruptions could also affect compliance with healthcare regulations requiring system availability and data integrity.

European healthcare organizations should implement strict controls on the provenance and validation of DICOM files, restricting file sources to trusted entities only. Employ sandboxing or isolated environments for opening untrusted DICOM files to contain potential crashes. Monitor and log application crashes related to DICOM processing to detect exploitation attempts. Since no official patches are currently available, organizations should track vendor advisories and apply updates promptly once released. Consider using alternative DICOM libraries or updated versions of GDCM that address this vulnerability. Implement robust input validation and fuzz testing in custom software that integrates GDCM. Network segmentation of medical imaging systems can limit exposure. Training staff to recognize suspicious files and avoid opening unknown DICOM files can reduce risk. Finally, maintain comprehensive backups and incident response plans to recover from potential service disruptions.