# CVE-2025-64181: PYSEC-2026-2843 - OpenEXR Makes Use of Uninitialized Memory

Source: https://junglewise.ai/threats/cve-2025-64181-openexr-use-of-uninitialized-memory-in-generic-unpack  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-13. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2025-64181 · Severity: low · CVSS 3.1 · Published 2026-07-13

OpenEXR is a widely-used library for reading and writing high-dynamic-range (HDR) image files. A vulnerability in the image decoding process causes the library to branch on uninitialized memory values when unpacking pixel data, which can lead to unpredictable behavior, application crashes, or denial of service when processing specially crafted EXR files.

Technologies: [OpenEXR (PyPI)](https://junglewise.ai/threats/technologies/openexr). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2025-64181 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-64181 being exploited in the wild.

**How severe is CVE-2025-64181?** Low severity, with a CVSS score of 3.1, published 13 July 2026.

**Which products and versions are affected?** OpenEXR (PyPI) ECOSYSTEM:introduced=3.3.0,fixed=3.3.6, ECOSYSTEM:introduced=3.3.0,fixed=3.3.6,introduced=3.4.0,fixed=3.4.3.

**Is there a fix for CVE-2025-64181?** Yes. OpenEXR (PyPI): upgrade to 3.3.6, 3.4.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-64181 attacked?** It is attacked over the network.

**Am I affected by CVE-2025-64181?** Check whether you run OpenEXR (PyPI) at an affected version. 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.

## How to fix

- OpenEXR (PyPI): upgrade to 3.3.6, 3.4.3 or later

  ```sh
  pip install "OpenEXR>=3.4.3"
  ```


## Technical details

The vulnerability is a use-of-uninitialized-memory (CWE-457) issue in the generic_unpack() function within the OpenEXR image decoding pipeline. The root cause is that a per-tile/per-scanline decode scratch buffer allocated via malloc during exr_decoding_run() is not fully initialized before being read, causing conditional branches to depend on uninitialized heap data. The vulnerability is triggered when processing malformed or specially crafted EXR files that do not fully populate the scratch buffer during decompression. An attacker can exploit this by providing a malicious EXR file that, when opened or validated by an application using OpenEXR, causes undefined behavior. The issue affects versions 3.3.0–3.3.5 and 3.4.0–3.4.2, and patches are available in versions 3.3.6 and 3.4.3.

## Affected products

- Academy Software Foundation OpenEXR 3.3.0-3.3.5, 3.4.0-3.4.2

## Identifiers

- CVE-2025-64181
- GHSA-3h9h-qfvw-98hq
- PYSEC-2026-2843

## Timeline

- 2025-11-08: disclosed
- 2026-04-06: patched: Versions 3.3.6 and 3.4.3 contain fixes

## References

- [https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-3h9h-qfvw-98hq](https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-3h9h-qfvw-98hq)

## Related threats

- [PYSEC-2026-2849 - OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp](https://junglewise.ai/threats/cve-2026-26981-openexr-has-heap-buffer-overflow-via-signed-integer-underflow-in)
- [PYSEC-2026-2844 - OpenEXR has use after free in PyObject_StealAttrString](https://junglewise.ai/threats/cve-2025-64183-openexr-has-use-after-free-in-pyobject-stealattrstring)
- [PYSEC-2026-2851 - OpenEXR has buffer overflow in PyOpenEXR_old's channels() and channel()](https://junglewise.ai/threats/cve-2025-64182-openexr-has-buffer-overflow-in-pyopenexr-old-s-channels-and)
- [PYSEC-2026-1748 - OpenEXR ScanLineProcess::run_fill NULL Pointer Write In "reduceMemory" Mode](https://junglewise.ai/threats/cve-2025-48073-openexr-scanlineprocess-run-fill-null-pointer-write-in)
- [PYSEC-2026-1746 - OpenEXR Out of Bounds Heap Read due to Bad Pointer Arithmetic in LossyDctDecoder_execute](https://junglewise.ai/threats/cve-2025-48072-openexr-out-of-bounds-heap-read-due-to-bad-pointer-arithmetic-in)