CVE-2026-42216 Overview
CVE-2026-42216 is an out-of-bounds read vulnerability [CWE-125] in OpenEXR, the reference implementation of the EXR image file format used widely in motion picture and visual effects pipelines. The flaw resides in IDManifest::init(), which reconstructs strings from a prefix-compressed representation. When a previous string exceeds 255 bytes, the parser reads stringList[i][0] and stringList[i][1] without verifying that the current string contains at least two bytes. A crafted EXR file can trigger memory reads beyond allocated bounds during parsing.
Critical Impact
A network-delivered malicious EXR file processed by a vulnerable OpenEXR build can cause confidentiality loss and process availability impact through out-of-bounds memory access.
Affected Products
- OpenEXR versions 3.0.0 to before 3.2.9
- OpenEXR versions 3.3.0 to before 3.3.11
- OpenEXR versions 3.4.0 to before 3.4.11
Discovery Timeline
- 2026-05-07 - CVE-2026-42216 published to NVD
- 2026-05-07 - Last updated in NVD database
Technical Details for CVE-2026-42216
Vulnerability Analysis
OpenEXR encodes ID manifest string tables using prefix compression to reduce file size. Each subsequent string reuses a prefix from the prior string and appends a suffix. The encoded length of the shared prefix is normally a single byte. When the previous string is longer than 255 bytes, the format switches to a two-byte prefix length to represent values that exceed an 8-bit range.
The parser in IDManifest::init() selects the two-byte path based on the previous string's length but does not validate that the current entry actually contains two readable bytes. The implementation indexes into stringList[i][0] and stringList[i][1] directly. If the buffer holds fewer than two bytes, the second read crosses the allocated boundary.
Processing an attacker-supplied EXR file is sufficient to reach the vulnerable code path. OpenEXR is embedded in compositing software, render engines, and image-processing libraries, so exposure extends to any application that ingests EXR content from untrusted sources.
Root Cause
The root cause is missing length validation before indexed buffer access. The decoder trusts the structural assumption that any entry following a long string carries a two-byte prefix header, without confirming the entry's own size. This is a classic out-of-bounds read pattern catalogued under [CWE-125].
Attack Vector
The attack vector is network-accessible. An adversary delivers a crafted EXR file through email, web upload, asset-sharing platforms, or any workflow that feeds EXR data to a vulnerable parser. No privileges or user interaction beyond opening the file are required. Exploitation can leak adjacent heap contents or terminate the host process.
No verified public proof-of-concept code is available. Refer to the GitHub Security Advisory GHSA-65j8-95g9-jgj4 for advisory-level technical detail.
Detection Methods for CVE-2026-42216
Indicators of Compromise
- Unexpected crashes or aborts in applications that load EXR files, particularly in functions referencing IDManifest symbols.
- EXR files received from untrusted sources containing oversized or malformed ID manifest sections.
- Anomalous memory access faults logged by host monitoring agents during image-processing workloads.
Detection Strategies
- Inventory build artifacts and dependencies for OpenEXR versions in the vulnerable ranges (3.0.0–3.2.8, 3.3.0–3.3.10, 3.4.0–3.4.10).
- Run software composition analysis against container images, application bundles, and rendering toolchains that statically link or vendor libOpenEXR.
- Apply fuzzing or sanitizer-equipped builds (AddressSanitizer) to validate EXR ingestion paths in custom tooling.
Monitoring Recommendations
- Monitor process telemetry for EDR-flagged crashes in rendering, compositing, and asset-pipeline executables.
- Alert on EXR files ingested from external email gateways, file-transfer services, or upload portals before they reach build agents.
- Track outbound network activity from image-processing hosts that could indicate post-exploitation behavior following memory disclosure.
How to Mitigate CVE-2026-42216
Immediate Actions Required
- Upgrade OpenEXR to version 3.2.9, 3.3.11, or 3.4.11 depending on the deployed branch.
- Rebuild and redeploy any application or container image that statically links the vulnerable library.
- Restrict ingestion of EXR files from untrusted sources until patched binaries are in place.
Patch Information
The Academy Software Foundation has published fixed releases at OpenEXR 3.2.9, 3.3.11, and 3.4.11. The patch adds bounds checks before reading the two-byte prefix length in IDManifest::init(). Details are documented in the GitHub Security Advisory GHSA-65j8-95g9-jgj4.
Workarounds
- Block or quarantine EXR files at email and web gateways pending remediation.
- Sandbox image-processing workloads using process isolation or container-level seccomp profiles to limit blast radius.
- Disable EXR import in applications that do not require the format.
# Verify the linked OpenEXR version on Linux build hosts
pkg-config --modversion OpenEXR
ldd /path/to/application | grep -i openexr
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
