# CVE-2026-39886: OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for…

Source: https://junglewise.ai/threats/cve-2026-39886-openexr-provides-the-specification-and-reference-implementation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-21  
License: CC BY 4.0 with a link back

CVE-2026-39886 · Severity: medium · CVSS 5.3 · Published 2026-04-21

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 `ht_undo_impl()` function in `src/lib/OpenEXRCore/internal_ht.cpp` accumulates a bytes-per-line value (`bpl`) 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 `bpl` to overflow `INT_MAX`, producing undefined behavior confirmed by UBSan. On an
allocator-permissive host where the required ~64 GB allocation succeeds, the wrapped negative `bpl` 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 `ht_undo_impl()` is entered. This is the second distinct integer overflow in `ht_undo_impl()`. CVE-2026-34545 addressed a different overflow in the same function — the `int16_t p` pixel-loop counter at line ~302 that overflows when iterating over channels whose `width` exceeds 32,767. The CVE-2026-34545 fix did not touch the `int bpl` accumulator at line 211, which is the subject of this advisory. The `bpl` 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 `wcount*nx` overflow in `internal_piz.c`) and should be remediated with the same pattern. The CVE-2026-34588 fix did not touch `internal_ht.cpp`. Version 3.4.10 contains a remediation that addresses the vulnerability in `internal_ht.cpp`.

Technologies: [Openexr](https://junglewise.ai/threats/technologies/openexr-openexr). Vendors: [Openexr](https://junglewise.ai/threats/vendors/openexr).

## Quick answers

**Is CVE-2026-39886 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39886 being exploited in the wild.

**How severe is CVE-2026-39886?** Medium severity, with a CVSS score of 5.3, published 21 April 2026.

**Which products and versions are affected?** Openexr. The advisory does not name versions.

**Is there a fix for CVE-2026-39886?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-39886?** Check whether you run Openexr. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Openexr

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