Findings

CVE-2026-39886

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry.

Published Apr 21, 2026 · updated Jun 17, 2026 · openexr openexr

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. Versions 3.4.0 through 3.4.9 have a signed integer overflow vulnerability in OpenEXR's HTJ2K (High-Throughput JPEG 2000) decompression path. The function in accumulates a bytes-per-line value ( ) using a 32-bit signed integer with no overflow guard. A crafted EXR file with 16,385 FLOAT channels at the HTJ2K maximum width of 32,767 causes to overflow , producing undefined behavior confirmed by UBSan. On an allocator-permissive host where the required ~64 GB allocation succeeds, the wrapped negative value would subsequently be used as a per-scanline pointer advance, which would produce a heap out-of-bounds write. On a memory-constrained host, the allocation fails before is entered. This is the second distinct integer overflow in . CVE-2026-34545 addressed a different overflow in the same function — the pixel-loop counter at line ~302 that overflows when iterating over channels whose exceeds 32,767. The CVE-2026-34545 fix did not touch the accumulator at line 211, which is the subject of this advisory. The accumulator was also not addressed by any of the 8 advisories in the 2026-04-05 v3.4.9 release batch. This finding is structurally identical to CVE-2026-34588 (PIZ overflow in ) and should be remediated with the same pattern. The CVE-2026-34588 fix did not touch . Version 3.4.10 contains a remediation that addresses the vulnerability in .