Orthanc DICOM Vulnerabilities Lead to Crashes, RCE

Nine vulnerabilities in the open source Digital Imaging and Communications in Medicine (DICOM) server Orthanc allow attackers to crash servers, leak data, and execute arbitrary code remotely. A lightweight standalone DICOM server for healthcare and medical research, Orthanc supports the automated analysis of medical images and does not require complex database administration or third-party dependencies. The nine security defects in Orthanc, tracked CVE-2026-5437 to CVE-2026-5445, are rooted in insufficient validation of metadata, missing checks, and unsafe arithmetic operations, CERT Coordination Center (CERT/CC) notes in an advisory. The first bug is an out-of-bounds read issue affecting the meta-header parser, caused by insufficient input validation in the parsing logic. Next is a GZIP decompression bomb flaw in the processing of specific HTTP requests. Because no limit is enforced on decompressed size, and memory is allocated based on attacker-controlled metadata, a malicious payload could be used to exhaust system memory. Another memory exhaustion defect was discovered in ZIP archive processing, where the server trusts metadata describing the uncompressed size of the archived files, allowing an attacker to forge size values and cause the server to allocate extremely large buffers during extraction. The HTTP server was also found to allocate memory directly based on user-supplied header values, allowing attackers to craft an HTTP request containing an extremely large length value, triggering server termination. Orthanc’s decompression routine for the proprietary Philips Compression format is affected by an out-of-bounds read vulnerability, where escape markers at the end of the compressed data stream are improperly validated. “A crafted sequence at the end of the buffer can cause the decoder to read beyond the allocated memory region and leak heap data into the rendered image output,” the CERT/CC advisory reads. Another out-of-bounds read weakness was identified in the lookup-table decoding logic for Palette Color images, which fails to validate pixel indices. The flaw can be exploited via crafted images with indices larger than the palette size. The last three security defects are heap buffer overflow issues impacting the image decoder, Palette Color image decoding logic, and PAM image parsing logic. Successful exploitation of these vulnerabilities could lead to out-of-bounds memory access. “The most severe issues are heap-based buffer overflows in image parsing and decoding logic, which can crash the Orthanc process and may, under certain conditions, provide a pathway to remote code execution (RCE),” the CERT/CC advisory reads. Orthanc versions 1.12.10 and earlier are affected by these bugs. Users are advised to update to version 1.12.11, which addresses all of them. The vulnerabilities were discovered by researchers at Machine Spirits, who published their own advisories.  Related: Critical Marimo Flaw Exploited Hours After Public Disclosure Related: Microsoft Finds Vulnerability Exposing Millions of Android Crypto Wallet Users Related: Data Leakage Vulnerability Patched in OpenSSL Related: RCE Bug Lurked in Apache ActiveMQ Classic for 13 Years WRITTEN BY Ionut Arghire Ionut Arghire is an international correspondent for SecurityWeek. 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