How severe is CVE-2025-64181?

No CVSS score has been assigned to CVE-2025-64181 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-64181?

CVE-2025-64181 affects the following packages: openexr (PyPI), openexr (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-64181?

Update openexr to 3.3.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64181 is resolved across your whole dependency graph.

How do I detect CVE-2025-64181 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openexr, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-64181 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-64181 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-64181 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-64181?

CVE-2025-64181 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 35th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-64181?

CVE-2025-64181 is classified as CWE-457 (CWE-457). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-64181 published, and has it been updated?

CVE-2025-64181 was published on November 10, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2025-64181 — openexr

CVE-2025-64181 is a CWE-457 vulnerability in openexr. A fix is available for openexr — see the affected versions and patch details below.

OpenEXR Makes Use of Uninitialized Memory

Also known asGHSA-3h9h-qfvw-98hqPYSEC-2026-2843

Published

Nov 10, 2025

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-64181.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs35th percentile — riskier than 35% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

🐍openexr🐍openexr

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

While fuzzing openexr_exrcheck_fuzzer, Valgrind reports a conditional branch depending on uninitialized data inside generic_unpack. This indicates a use of uninitialized memory (CWE-457). The issue is reproducible with the current OSS-Fuzz harness and a single-file PoC.

Details

Environment:

Tooling: valgrind --tool=memcheck --track-origins=yes
Target: openexr_exrcheck_fuzzer
OS: Ubuntu 20.04.6 LTS focal x86_64
openexr version and Git-commit hash: openexr 3.4.2 | commit fd657e8a41e157e5841c7cc2e2a5efe094b069a1 (grafted, HEAD -> main, origin/main, origin/HEAD)

Function: generic_unpack

Possible root cause (based on observed symptoms): The unpacker is branching on bytes in a scratch buffer that were never written because the decode step didn’t fully populate it.

The first use flagged is in generic_unpack(). That function reads from the decompressed/expanded pixel buffer to scatter data into the framebuffer. A “conditional jump depends on uninitialised value(s)” means it’s consulting bytes in that buffer before they were written.
Valgrind says the uninitialised value “was created by a heap allocation (malloc)”, not the stack: this matches a per-tile/per-scanline decode scratch buffer allocated in exr_decoding_run().

Valgrind Trace (top frames):

==454== Conditional jump or move depends on uninitialised value(s)
==454==    at 0x4539BE: generic_unpack (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x44B85F: exr_decoding_run (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x38BC5F: Imf_4_0::(anonymous namespace)::TileProcess::run_decode(_priv_exr_context_t const*, int, Imf_4_0::FrameBuffer const*, std::__1::vector<Imf_4_0::Slice, std::__1::allocator<Imf_4_0::Slice> > const&) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x388BE1: Imf_4_0::TiledInputFile::Data::readTiles(int, int, int, int, int, int) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x388619: Imf_4_0::TiledInputFile::readTiles(int, int, int, int, int, int) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x353755: Imf_4_0::InputFile::Data::bufferedReadPixels(int, int) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x352286: Imf_4_0::InputFile::readPixels(int) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x3190FA: Imf_4_0::(anonymous namespace)::readMultiPart(Imf_4_0::MultiPartInputFile&, bool, bool) (in /out/openexr_exrcheck_fuzzer)
==454==    by 0x314C4D: Imf_4_0::checkOpenEXRFile(char const*, unsigned long, bool, bool, bool) (in /out/openexr_exrcheck_fuzzer)
==454==  Uninitialised value was created by a heap allocation at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)

PoC

In the attached archive, you will find:

The executable used for our tests.
The testcase used to trigger the bug.

To observe the bug, simply run the OSS-Fuzz helper script:

git clone https://github.com/google/oss-fuzz.git
cd oss-fuzz

python3 infra/helper.py build_image openexr
python3 infra/helper.py build_fuzzers --sanitizer=none openexr
python3 infra/helper.py shell openexr

apt update && apt install -y valgrind
ulimit -n 65535
valgrind --tool=memcheck --track-origins=yes /out/openexr_exrcheck_fuzzer /path/to/poc

Impact

Undefined Behavior
Potential crash
Denial of Service

Credit: Aldo Ristori archive0.zip

Update Note:

Other saved testcases from the fuzzing campaign trigger the same underlying bug, but with a different manifestation. So there is one root cause (missing post-decode validation / zero-init before any unpack), with different call-sites. Below there are several archives, formatted like the previous one, that reproduce the other test cases.

Other observed sinks (distinct manifestations of the same bug):

Deep pointers path: generic_unpack_deep_pointers (deep scanline/tiled) archive1.zip

Deep sample table path: unpack_sample_table (deep scanline) archive2.zip

Half conversion path: half_to_float_buffer_f16c via unpack_half_to_float_3chan_planar archive3.zip

Deep compositing: CompositeDeepScanLine::readPixels → ThreadPool::addTask → LineCompositeTask::execute archive4.zip

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`openexr`	≥ 3.3.0&&< 3.3.6	3.3.6`pip install --upgrade 'openexr==3.3.6'`
🐍PyPI	`openexr`	≥ 3.4.0&&< 3.4.3	3.4.3`pip install --upgrade 'openexr==3.4.3'`

Affected Products

1 product · 2 configurations

Application

openexropenexr

≥ 3.4.0 && < 3.4.3

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openexr, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update openexr to 3.3.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64181 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

This vulnerability affects all OpenEXR versions beginning with 3.1.0 (https://github.com/AcademySoftwareFoundation/openexr/commit/a04cbf5a48c7a8b6a6dd3b1e2471bde3cd4cb6df), when the new C-based EXR decoding backend was first introduced. Any release that includes this backend inherits the vulnerable generic_unpack…

Workaround published by Red Hat

No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.

Source: Red Hat security advisory for CVE-2025-64181 (CC BY 4.0)

Frequently Asked Questions

### Summary While fuzzing `openexr_exrcheck_fuzzer`, Valgrind reports a conditional branch depending on uninitialized data inside `generic_unpack`. This indicates a use of uninitialized memory (CWE-457). The issue is reproducible with the current OSS-Fuzz harness and a single-file PoC. ### Details **Environment:** - Tooling: `valgrind --tool=memcheck --track-origins=yes` - Target: `openexr_exrcheck_fuzzer` - OS: Ubuntu 20.04.6 LTS focal x86_64 - openexr version and Git-commit hash: ` openexr 3.4.2 | commit fd657e8a41e157e5841c7cc2e2a5efe094b069a1 (grafted, HEAD -> main, origin/main, origin/H