The vulnerability identified as CVE-2026-26981 affects the openexr library, a widely used open-source implementation of the EXR image file format, primarily utilized in the motion picture and visual effects industries. The issue is a heap-buffer-overflow caused by a signed to unsigned integer conversion error within the istream_nonparallel_read function in the ImfContextInit.cpp source file. Specifically, when parsing a malformed EXR file through a memory-mapped IStream, a signed integer subtraction results in a negative value. This negative value is implicitly converted to an unsigned size_t type, which leads to an abnormally large length being passed to memcpy, causing an out-of-bounds read on the heap. This can trigger application crashes or potentially be leveraged for denial of service attacks. The vulnerability affects openexr versions from 3.3.0 up to but not including 3.3.7, and from 3.4.0 up to but not including 3.4.5. The flaw does not require privileges or authentication but does require user interaction to open a maliciously crafted EXR file. The CVSS v3.1 base score is 6.5, reflecting medium severity with network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, no confidentiality or integrity impact, but high impact on availability. The issue has been patched in versions 3.3.7 and 3.4.5. No known exploits have been reported in the wild to date.

This vulnerability primarily impacts applications and workflows that utilize the openexr library to process EXR image files, especially in the motion picture, animation, and visual effects industries. Exploitation can lead to application crashes or denial of service, disrupting production pipelines and potentially causing downtime in rendering or image processing systems. While there is no direct impact on confidentiality or integrity, the availability impact can be significant in environments relying heavily on automated image processing. Attackers could craft malicious EXR files that, when opened or processed, trigger the vulnerability. Because the flaw requires user interaction to open a malicious file, the risk is somewhat mitigated but remains relevant in environments where untrusted EXR files are handled. Organizations with automated ingestion of EXR files from external sources or collaborative workflows involving third-party content are at higher risk. The absence of known exploits reduces immediate threat but patching is critical to prevent future exploitation.

Organizations should upgrade openexr to versions 3.3.7 or 3.4.5 or later, where the vulnerability is patched. Until upgrades can be applied, implement strict validation and sanitization of EXR files from untrusted sources before processing. Employ sandboxing or isolation techniques for applications that parse EXR files to limit the impact of potential crashes or exploitation attempts. Monitor logs and application behavior for crashes or anomalies related to EXR file processing. Educate users and teams to avoid opening EXR files from untrusted or unknown origins. If automated pipelines ingest EXR files, consider adding file integrity checks or scanning for malformed files using specialized tools. Maintain up-to-date backups and incident response plans to quickly recover from potential denial of service incidents. Finally, track vendor advisories for any updates or additional patches.