CVE-2026-27622 — OpenEXR CompositeDeepScanLine integer-overflow leads to heap OOB write

Affected: AcademySoftwareFoundation openexr, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8.2 Advanced Update Support, Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Telecommunications Update Service, Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions and 10 more

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In CompositeDeepScanLine::readPixels, per-pixel totals are accumulated in vector<unsigned int> total_sizes for attacker-controlled large counts across many parts, total_sizes[ptr] wraps modulo 2^32. overall_sample_count is then derived from wrapped totals and used in samples[channel].resize(overall_sample_count). Decode pointer setup/consumption proceeds with true sample counts, and write operations in core unpack (generic_unpack_deep_pointers) overrun the undersized composite sample buffer. This vulnerability is fixed in v3.2.6, v3.3.8, and v3.4.6.

GHSA-cr4v-6jm6-4963 — OpenEXR's CompositeDeepScanLine integer-overflow leads to heap OOB write

Affected: PyPI: OpenEXR

## Summary

Function: `CompositeDeepScanLine::readPixels`, reachable from high-level multipart deep read flows (`MultiPartInputFile` + `DeepScanLineInputPart` + `CompositeDeepScanLine`).

Vulnerable lines (`src/lib/OpenEXR/ImfCompositeDeepScanLine.cpp`): - `total_sizes[ptr] += counts[j][ptr];` (line ~511) - `overall_sample_count += total_sizes[ptr];` (line ~514) - `samples[channel].resize (overall_sample_count);` (line ~535)

Impact: 32-bit sample-count accumulation wrap leads to undersized allocation, then decode writes with true sample volume, causing heap OOB write in `generic_unpack_deep_pointers` (`src/lib/OpenEXRCore/unpack.c:1374`) (DoS/Crash, memory corruption/RCE).

Attack scenario: - Attacker provides multipart deep EXR with many parts and very large sample counts per pixel. - Uses compression (RLE/ZIPS) to keep file size relatively small vs decode pressure. - The overflow happens in composite sample accounting (`unsigned int`), while pointer progression for decode uses larger counters and reaches out-of-bounds.

Tested on: `OpenEXR 4.0.0-dev` (commit 83449669402080874b25ff1fa740649a9e6ea064) but this code has existed since v2.3.0

## Steps to reproduce

[composite_deepscanline_poc_bundle.patch](https://github.com/user-attachments/files/25383205/composite_deepscanline_poc_bundle.patch)

PoC files used: - Writer/generator: `poc/composite_deep_scanline_e2e_compressed_poc.cpp` - Minimal high-level reader harness: `poc/simple_exr_reader.cpp`

The reader harness intenti…

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CVE-2026-27622 — OpenEXR CompositeDeepScanLine integer-overflow leads to heap OOB write

GHSA-cr4v-6jm6-4963 — OpenEXR's CompositeDeepScanLine integer-overflow leads to heap OOB write