CVE-2026-5443: DICOM Image Buffer Overflow Vulnerability

CVE-2026-5443 Overview

A heap buffer overflow vulnerability exists during the decoding of PALETTE COLOR DICOM images. The vulnerability stems from improper pixel length validation that uses 32-bit multiplication for width and height calculations. When these values overflow, the validation check incorrectly succeeds, allowing the decoder to read and write to memory beyond allocated buffers.

Critical Impact

Attackers can exploit this integer overflow to trigger heap buffer overflow conditions, potentially leading to arbitrary code execution or denial of service in medical imaging systems that process DICOM files.

Affected Products

• DICOM image processing libraries
• Medical imaging servers and viewers
• Healthcare systems processing PALETTE COLOR DICOM images

Discovery Timeline

• 2026-04-09 - CVE CVE-2026-5443 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-5443

Vulnerability Analysis

This heap buffer overflow vulnerability affects the image decoding process for DICOM files that use the PALETTE COLOR photometric interpretation. The root issue lies in the arithmetic operations performed during pixel buffer allocation and validation.

When a DICOM image decoder processes PALETTE COLOR images, it must calculate the total buffer size required based on the image dimensions (width × height × bytes per pixel). The vulnerable implementation performs this calculation using 32-bit integer arithmetic, which creates an integer overflow condition when processing images with carefully crafted dimensions.

For example, if an attacker provides image dimensions where width × height × bytes_per_pixel exceeds the maximum value representable in a 32-bit integer (4,294,967,295), the multiplication wraps around to a smaller value. This truncated result passes the size validation check, causing the decoder to allocate a buffer that is significantly smaller than required.

Subsequently, when the decoder attempts to read pixel data into this undersized buffer, it writes beyond the allocated heap memory, resulting in heap corruption. This memory corruption can be leveraged by sophisticated attackers to achieve arbitrary code execution or cause denial of service conditions in medical imaging systems.

Root Cause

The vulnerability originates from unsafe integer arithmetic in the pixel buffer size calculation. The decoder uses 32-bit multiplication to compute width × height without checking for integer overflow conditions before the multiplication. When the product exceeds 2^32-1, the result wraps around, producing a small value that passes validation but does not reflect the actual memory requirements for storing the image data.

Attack Vector

An attacker can exploit this vulnerability by crafting a malicious DICOM file containing:

1. A PALETTE COLOR photometric interpretation marker
2. Excessively large width and height values designed to cause integer overflow when multiplied
3. Pixel data that, when decoded, writes beyond the undersized heap buffer

The attack requires the victim to process the malicious DICOM file. In healthcare environments, this could occur through:

• Importing studies from external media or network sources
• Receiving DICOM images through PACS (Picture Archiving and Communication System) workflows
• Processing images uploaded through web-based medical imaging portals

The exploitation mechanism involves carefully selecting width and height values such that their product overflows to a small number, triggering an undersized allocation followed by an out-of-bounds heap write during pixel decoding. For detailed technical analysis, refer to the CERT Vulnerability Advisory #536588.

Detection Methods for CVE-2026-5443

Indicators of Compromise

• DICOM files with unusually large width or height dimension values in image headers
• Abnormal memory allocation patterns or crashes in DICOM processing services
• System logs indicating heap corruption or segmentation faults during image decoding operations

Detection Strategies

• Monitor DICOM server logs for processing errors related to PALETTE COLOR images with anomalous dimensions
• Implement input validation to detect DICOM files with width/height values that would cause integer overflow when multiplied
• Deploy memory safety monitoring tools to detect heap overflow attempts in medical imaging applications
• Use file integrity monitoring on DICOM storage directories to identify potentially malicious files

Monitoring Recommendations

• Enable verbose logging for DICOM image processing operations to capture dimension parameters
• Configure alerting for crashes or unexpected terminations of medical imaging services
• Implement network-level monitoring for DICOM traffic containing suspicious image metadata
• Review system event logs for heap corruption indicators in imaging application processes

How to Mitigate CVE-2026-5443

Immediate Actions Required

• Review and update DICOM processing libraries used in medical imaging infrastructure
• Implement input validation to reject DICOM images with dimension values that could cause integer overflow
• Consider isolating DICOM processing services in sandboxed environments to limit exploitation impact
• Apply available security patches from DICOM library vendors

Patch Information

Organizations should monitor vendor security advisories and apply patches as they become available. Technical details and updates can be found through the CERT Vulnerability Advisory #536588. Additionally, operators using Orthanc Server or similar DICOM implementations should consult their respective documentation for security guidance.

Workarounds

• Implement pre-processing validation that checks for integer overflow in width × height calculations before passing DICOM files to vulnerable decoders
• Use 64-bit arithmetic for dimension calculations to prevent overflow conditions
• Deploy application-level firewalls or content inspection systems to filter DICOM files with suspicious dimension values
• Restrict DICOM file imports to trusted sources until patches are applied

# Example validation check for DICOM dimensions
# Reject images where width * height would overflow 32-bit integer
MAX_SAFE_DIMENSION=65535
if [ "$width" -gt "$MAX_SAFE_DIMENSION" ] || [ "$height" -gt "$MAX_SAFE_DIMENSION" ]; then
    echo "Warning: DICOM image dimensions exceed safe threshold"
    exit 1
fi