CVE-2026-27622: OpenEXR Buffer Overflow Vulnerability

CVE-2026-27622 Overview

CVE-2026-27622 is an integer overflow vulnerability in OpenEXR, the specification and reference implementation of the EXR file format widely used in the motion picture industry. The vulnerability exists in the CompositeDeepScanLine::readPixels function where per-pixel totals are accumulated in a vector<unsigned int> called total_sizes. When processing attacker-controlled large counts across many parts, the total_sizes[ptr] value wraps modulo 2^32, causing subsequent buffer allocations to be undersized. This leads to an out-of-bounds write condition when the true sample counts are used during decode operations.

Critical Impact

Successful exploitation of this vulnerability could allow attackers to achieve arbitrary code execution by crafting malicious EXR image files that trigger heap buffer overflows during image processing operations.

Affected Products

• OpenEXR versions prior to 3.2.6
• OpenEXR versions 3.3.x prior to 3.3.8
• OpenEXR versions 3.4.x prior to 3.4.6

Discovery Timeline

• 2026-03-03 - CVE-2026-27622 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-27622

Vulnerability Analysis

This vulnerability represents a classic integer overflow condition that leads to a heap buffer overflow (CWE-787). The root cause lies in the accumulation of per-pixel sample counts using 32-bit unsigned integers, which can overflow when processing specially crafted EXR files with excessively large counts distributed across multiple parts.

When the CompositeDeepScanLine::readPixels function processes deep scanline data, it accumulates sample counts in the total_sizes vector. An attacker can craft an EXR file with carefully calculated counts that cause this accumulator to wrap around to a small value due to 32-bit integer overflow. The overall_sample_count derived from these wrapped totals is then used to allocate the sample buffer via samples[channel].resize(overall_sample_count), resulting in a buffer that is significantly smaller than required.

Subsequently, when the decode pointer setup and consumption proceeds with the true (unwrapped) sample counts, write operations in the core unpack function (generic_unpack_deep_pointers) overrun the undersized composite sample buffer, leading to heap corruption.

Root Cause

The vulnerability stems from insufficient bounds checking when accumulating pixel sample counts in 32-bit unsigned integer variables. The total_sizes vector uses unsigned int elements, which on most platforms are 32 bits. When an attacker provides EXR data with extremely large sample counts across multiple parts, the arithmetic addition causes integer wraparound, resulting in an incorrectly small allocation size that does not match the actual data requirements.

Attack Vector

Exploitation requires user interaction where a victim opens a maliciously crafted EXR image file. The attack is local in nature, meaning the attacker must deliver the malicious file to the target system through phishing, file sharing, or other social engineering techniques. Once the victim opens the file with an application using a vulnerable OpenEXR library, the integer overflow triggers during the deep scanline pixel reading operation.

The vulnerability is particularly concerning for applications in the visual effects and motion picture industries where EXR files are routinely exchanged between vendors, studios, and artists. An attacker could embed a malicious EXR file within a larger production workflow, potentially compromising systems involved in film or game production pipelines.

Detection Methods for CVE-2026-27622

Indicators of Compromise

• Presence of EXR files with abnormally large deep sample counts in file metadata
• Application crashes in OpenEXR library functions, particularly CompositeDeepScanLine::readPixels or generic_unpack_deep_pointers
• Unexpected memory allocation patterns or heap corruption errors when processing EXR files
• Core dumps or crash reports indicating heap buffer overflows in image processing applications

Detection Strategies

• Monitor for unusual EXR file processing behavior including excessive memory allocation requests
• Implement application-level sandboxing for image processing workloads to contain potential exploitation
• Deploy endpoint detection rules targeting heap overflow patterns in OpenEXR-dependent applications
• Review application logs for crashes or exceptions during EXR file parsing operations

Monitoring Recommendations

• Enable crash reporting and core dump analysis for applications utilizing OpenEXR libraries
• Implement file integrity monitoring for incoming EXR files in production pipelines
• Configure memory protection mechanisms such as ASLR and stack canaries to mitigate exploitation
• Monitor network traffic for unusual EXR file transfers that may indicate targeted attacks

How to Mitigate CVE-2026-27622

Immediate Actions Required

• Upgrade OpenEXR to patched versions 3.2.6, 3.3.8, or 3.4.6 immediately
• Audit all applications and dependencies that utilize the OpenEXR library
• Restrict processing of untrusted EXR files until patches are applied
• Implement input validation to reject EXR files with suspicious metadata characteristics

Patch Information

The OpenEXR project has released security updates addressing this vulnerability. Users should upgrade to one of the following fixed versions based on their current release branch:

• Version 3.2.6 for users on the 3.2.x branch
• Version 3.3.8 for users on the 3.3.x branch
• Version 3.4.6 for users on the 3.4.x branch

For detailed patch information and upgrade instructions, refer to the OpenEXR Security Advisory.

Workarounds

• Avoid processing EXR files from untrusted sources until patches can be applied
• Implement application sandboxing to isolate EXR processing from critical system components
• Use alternative image formats where possible for untrusted content
• Deploy network-level filtering to block potentially malicious EXR files at ingress points

# Verify installed OpenEXR version
pkg-config --modversion OpenEXR

# For systems using apt package manager
apt list --installed | grep openexr

# Update to patched version via package manager
sudo apt update && sudo apt upgrade libopenexr-dev