CVE-2026-34589: OpenEXR DWA Lossy Decoder Heap Out-of-Bounds Vulnerability

Q: What is CVE-2026-34589?

CVE-2026-34589 is a security vulnerability in OpenEXR involving DWA Lossy Decoder Heap Out-of-Bounds Write under CWE-190: Integer Overflow or Wraparound.

Q: Which OpenEXR versions are affected?

Affected versions include releases prior to 3.2.7, 3.3.9, 3.4.9 across affected packages: OpenEXR.

Q: What version fixes CVE-2026-34589?

Upgrading to 3.2.7, 3.3.9, 3.4.9 (or the latest patched release for your respective branch) resolves the vulnerability.

Q: Is OpenEXR affected?

Yes, OpenEXR is affected in releases prior to 3.2.7, 3.3.9, 3.4.9. Upgrade your dependency to 3.2.7, 3.3.9, 3.4.9 or later.

Q: What is the CVSS score of CVE-2026-34589?

CVE-2026-34589 has a CVSS v3.1 base score of 5.0 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H.

Q: What CWE is associated with CVE-2026-34589?

CVE-2026-34589 is classified under CWE-190: Integer Overflow or Wraparound (The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.).

Q: How can I check PyPI dependencies for CVE-2026-34589?

Run the dependency tree command: 'pip show OpenEXR'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.

HIGH

Advisory Identifier: GHSA-p8xc-w3q4-h64x

CVSS 5.0

CWE-190 CWE-787

Published 2026-04-08

Advisory Summary

CVE-2026-34589 is a HIGH (CVSS 5.0) dwa lossy decoder heap out-of-bounds vulnerability (CWE-190: Integer Overflow or Wraparound) affecting OpenEXR libraries in the PyPI ecosystem. The issue involves dwa lossy decoder heap out-of-bounds write. Remediation is available by upgrading affected packages to version 3.2.7, 3.3.9, 3.4.9.

CVE-2026-34589 at a Glance

CVE Identifier CVE-2026-34589

GHSA Identifier GHSA-p8xc-w3q4-h64x

Severity HIGH

CVSS v3.1 Base Score 5.0

CWE Classification CWE-190: Integer Overflow or Wraparound

Affected Product OpenEXR

Package Ecosystem PyPI

Published Date 2026-04-08

Last Updated 2026-04-08

Security Impact

CVSS: 5.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H).

Attack Vector Local (AV:L)

Attack Complexity Low (AC:L)

Privileges Required Low (PR:L)

User Interaction Required (UI:R)

Scope Unchanged (S:U)

Confidentiality None (C:N)

Integrity None (I:N)

Availability High (A:H)

How to Fix CVE-2026-34589

To remediate this vulnerability, upgrade all affected OpenEXR dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

OpenEXR fixed: 3.2.7

pip install OpenEXR>=3.2.7

OpenEXR fixed: 3.3.9

pip install OpenEXR>=3.3.9

OpenEXR fixed: 3.4.9

pip install OpenEXR>=3.4.9

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release:

pip show OpenEXR

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-34589, inspect your installed packages using pip:

pip show OpenEXR

Analyze the terminal output to locate any version of OpenEXR in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.2.7), your application is affected.

Note: The pip show OpenEXR command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-190: Integer Overflow or Wraparound, where the product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. this occurs when an integer value is incremented to a value that is too large to store in the associated representation. when this occurs, the value may become a very small or negative number. In OpenEXR, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Summary The DWA lossy decoder constructs temporary per-component block pointers using signed 32-bit arithmetic. For a large enough width, the calculation overflows and later decoder stores operate on a wrapped pointer outside the allocated `rowBlock` backing store. This bug is reachable from the public decoder path and can be reproduced through the shipped `exrcheck` tool with a crafted scanline DWAA file. The confirmed dynamic symptom is a write-side crash in the lossy DCT execution path. Tested on commit: 7820b7e1b93405ba1d551c43a945018226b75bc5 ## Root Cause and Data Flow The vulnerable pointer construction lives in `src/lib/OpenEXRCore/internal_dwa_decoder.h`: ```c for (int comp = 1; comp < numComp; ++comp) rowBlock[comp] = rowBlock[comp - 1] + numBlocksX * 64; ``` The expression `numBlocksX * 64` is computed as signed `int`. Once `numBlocksX` is large enough, the multiplication wraps, and `rowBlock[comp]` points backward rather than forward into the temporary decode buffer. Later, `LossyDctDecoder_execute()` uses those derived pointers for real loads and stores during the block shuffle and reconstruction process. At that point the decoder is no longer operating within the bounds of the allocation created for `rowBlockHandle`. The public control flow is the standard one: ```c InputFile / ScanLineInputFile public read -> exr_decoding_run(...) -> exr_uncompress_chunk(...) -> internal_exr_undo_dwaa(...) -> DwaCompressor_uncompress(...) -> LossyDctDecoder_execute(...) ``` UBSan gives a clean root-cause diagnosis on the overflowing multiply, while ASAN shows the later memory error in the write-side decode path. ## Reproduction [dwa_scanline_exrcheck.zip](https://github.com/user-attachments/files/26318786/dwa_scanline_exrcheck.zip) Build with `exrcheck` with ASAN and run: ``` ❯ ./build-asan/bin/exrcheck /tmp/dwa_scanline_exrcheck.exr file /tmp/dwa_scanline_exrcheck.exr /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:331:58: runtime error: signed integer overflow: 33554432 * 64 cannot be represented in type 'int' AddressSanitizer:DEADLYSIGNAL ================================================================= ==1684058==ERROR: AddressSanitizer: SEGV on unknown address 0x758f8e5f0800 (pc 0x75979e850336 bp 0x7ffe8f1d3420 sp 0x7ffe8f1d30f0 T0) ==1684058==The signal is caused by a WRITE memory access. #0 0x75979e850336 in LossyDctDecoder_execute /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:524 #1 0x75979e879592 in DwaCompressor_uncompress /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_compressor.h:1210 #2 0x75979e879592 in internal_exr_undo_dwaa /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa.c:231 #3 0x75979e95f878 in exr_uncompress_chunk /home/pop/sec/openexr/src/lib/OpenEXRCore/compression.c:542 #4 0x75979e9659a8 in exr_decoding_run /home/pop/sec/openexr/src/lib/OpenEXRCore/decoding.c:580 #5 0x7597a0271add in run_decode /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:586 #6 0x7597a0283dc4 in Imf_4_0::ScanLineInputFile::Data::readPixels(Imf_4_0::FrameBuffer const&, int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:500 #7 0x7597a00c6a81 in Imf_4_0::InputFile::Data::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfInputFile.cpp:458 #8 0x7597a13fe2dc in readScanline<Imf_4_0::InputPart> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:239 #9 0x7597a1405b04 in readMultiPart /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:905 #10 0x7597a14126fd in runChecks<char const*> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1171 #11 0x7597a14146b9 in Imf_4_0::checkOpenEXRFile(char const*, bool, bool, bool) /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1835 #12 0x61ba9582b8f8 in exrCheck(char const*, bool, bool, bool, bool) /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:96 #13 0x61ba958282b1 in main /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:164 #14 0x75979d62a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58 #15 0x75979d62a28a in __libc_start_main_impl ../csu/libc-start.c:360 #16 0x61ba95829844 in _start (/home/pop/sec/openexr/build-asan/bin/exrcheck+0xe844) (BuildId: 087c972343a5372940c42c0a2e7bce4a84288aec) AddressSanitizer can not provide additional info. SUMMARY: AddressSanitizer: SEGV /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:524 in LossyDctDecoder_execute ==1684058==ABORTING ``` ------- Found by: Quang Luong of Calif.io

CVE-2026-34589 Affected OpenEXR Versions

3 component(s)

Fixed Versions:

3.2.73.3.93.4.9

Product / Package	Ecosystem	Affected Versions	Fixed Version
OpenEXR pypi/OpenEXR	PyPI	≥ 3.2.0 < 3.2.7	3.2.7
OpenEXR pypi/OpenEXR	PyPI	≥ 3.3.0 < 3.3.9	3.3.9
OpenEXR pypi/OpenEXR	PyPI	≥ 3.4.0 < 3.4.9	3.4.9

References

GitHub Advisory / Wiki ADVISORY

https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-p8xc-w3q4-h64x

NVD — CVE-2026-34589 NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-34589

OpenEXR Source Repository REPOSITORY

https://github.com/AcademySoftwareFoundation/openexr

OpenEXR Release RELEASE

https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7

OpenEXR Release RELEASE

https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.9

OpenEXR Release RELEASE

https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.4.9

Frequently Asked Questions

What is CVE-2026-34589?

CVE-2026-34589 is a security vulnerability in OpenEXR involving DWA Lossy Decoder Heap Out-of-Bounds Write under CWE-190: Integer Overflow or Wraparound.

Which OpenEXR versions are affected?

Affected versions include releases prior to 3.2.7, 3.3.9, 3.4.9 across affected packages: OpenEXR.

What version fixes CVE-2026-34589?

Upgrading to 3.2.7, 3.3.9, 3.4.9 (or the latest patched release for your respective branch) resolves the vulnerability.

Is OpenEXR affected?

Yes, OpenEXR is affected in releases prior to 3.2.7, 3.3.9, 3.4.9. Upgrade your dependency to 3.2.7, 3.3.9, 3.4.9 or later.

What is the CVSS score of CVE-2026-34589?

CVE-2026-34589 has a CVSS v3.1 base score of 5.0 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H.

What CWE is associated with CVE-2026-34589?

CVE-2026-34589 is classified under CWE-190: Integer Overflow or Wraparound (The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.).

How can I check PyPI dependencies for CVE-2026-34589?

Run the dependency tree command: 'pip show OpenEXR'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.

Machine-readable OSV JSON OSV v1.5 Schema

Normalized schema output

View Raw JSON

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-p8xc-w3q4-h64x",
  "modified" : "2026-04-08T15:09:05Z",
  "published" : "2026-04-08T15:09:05Z",
  "aliases" : [ "CVE-2026-34589" ],
  "summary" : "OpenEXR: DWA Lossy Decoder Heap Out-of-Bounds Write",
  "details" : "## Summary\n\nThe DWA lossy decoder constructs temporary per-component block pointers using signed 32-bit arithmetic. For a large enough width, the calculation overflows and later decoder stores operate on a wrapped pointer outside the allocated `rowBlock` backing store.\n\nThis bug is reachable from the public decoder path and can be reproduced through the shipped `exrcheck` tool with a crafted scanline DWAA file. The confirmed dynamic symptom is a write-side crash in the lossy DCT execution path.\n\nTested on commit: 7820b7e1b93405ba1d551c43a945018226b75bc5\n\n## Root Cause and Data Flow\n\nThe vulnerable pointer construction lives in `src/lib/OpenEXRCore/internal_dwa_decoder.h`:\n\n```c\nfor (int comp = 1; comp < numComp; ++comp)\n    rowBlock[comp] = rowBlock[comp - 1] + numBlocksX * 64;\n```\n\nThe expression `numBlocksX * 64` is computed as signed `int`. Once `numBlocksX` is large enough, the multiplication wraps, and `rowBlock[comp]` points backward rather than forward into the temporary decode buffer.\n\nLater, `LossyDctDecoder_execute()` uses those derived pointers for real loads and stores during the block shuffle and reconstruction process. At that point the decoder is no longer operating within the bounds of the allocation created for `rowBlockHandle`.\n\nThe public control flow is the standard one:\n\n```c\nInputFile / ScanLineInputFile public read\n  -> exr_decoding_run(...)\n     -> exr_uncompress_chunk(...)\n        -> internal_exr_undo_dwaa(...)\n           -> DwaCompressor_uncompress(...)\n              -> LossyDctDecoder_execute(...)\n```\n\nUBSan gives a clean root-cause diagnosis on the overflowing multiply, while ASAN shows the later memory error in the write-side decode path.\n\n## Reproduction\n\n[dwa_scanline_exrcheck.zip](https://github.com/user-attachments/files/26318786/dwa_scanline_exrcheck.zip)\n\nBuild with `exrcheck` with ASAN and run:\n\n```\n❯ ./build-asan/bin/exrcheck /tmp/dwa_scanline_exrcheck.exr\n file /tmp/dwa_scanline_exrcheck.exr /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:331:58: runtime error: signed integer overflow: 33554432 * 64 cannot be represented in type 'int'\nAddressSanitizer:DEADLYSIGNAL\n=================================================================\n==1684058==ERROR: AddressSanitizer: SEGV on unknown address 0x758f8e5f0800 (pc 0x75979e850336 bp 0x7ffe8f1d3420 sp 0x7ffe8f1d30f0 T0)\n==1684058==The signal is caused by a WRITE memory access.\n    #0 0x75979e850336 in LossyDctDecoder_execute /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:524\n    #1 0x75979e879592 in DwaCompressor_uncompress /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_compressor.h:1210\n    #2 0x75979e879592 in internal_exr_undo_dwaa /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa.c:231\n    #3 0x75979e95f878 in exr_uncompress_chunk /home/pop/sec/openexr/src/lib/OpenEXRCore/compression.c:542\n    #4 0x75979e9659a8 in exr_decoding_run /home/pop/sec/openexr/src/lib/OpenEXRCore/decoding.c:580\n    #5 0x7597a0271add in run_decode /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:586\n    #6 0x7597a0283dc4 in Imf_4_0::ScanLineInputFile::Data::readPixels(Imf_4_0::FrameBuffer const&, int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:500\n    #7 0x7597a00c6a81 in Imf_4_0::InputFile::Data::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfInputFile.cpp:458\n    #8 0x7597a13fe2dc in readScanline<Imf_4_0::InputPart> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:239\n    #9 0x7597a1405b04 in readMultiPart /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:905\n    #10 0x7597a14126fd in runChecks<char const*> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1171\n    #11 0x7597a14146b9 in Imf_4_0::checkOpenEXRFile(char const*, bool, bool, bool) /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1835\n    #12 0x61ba9582b8f8 in exrCheck(char const*, bool, bool, bool, bool) /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:96\n    #13 0x61ba958282b1 in main /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:164\n    #14 0x75979d62a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58\n    #15 0x75979d62a28a in __libc_start_main_impl ../csu/libc-start.c:360\n    #16 0x61ba95829844 in _start (/home/pop/sec/openexr/build-asan/bin/exrcheck+0xe844) (BuildId: 087c972343a5372940c42c0a2e7bce4a84288aec)\n\nAddressSanitizer can not provide additional info.\nSUMMARY: AddressSanitizer: SEGV /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_dwa_decoder.h:524 in LossyDctDecoder_execute\n==1684058==ABORTING\n```\n-------\nFound by: Quang Luong of Calif.io",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "OpenEXR"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.2.0"
      }, {
        "fixed" : "3.2.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "OpenEXR"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.3.0"
      }, {
        "fixed" : "3.3.9"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "OpenEXR"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.4.0"
      }, {
        "fixed" : "3.4.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-p8xc-w3q4-h64x"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34589"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/AcademySoftwareFoundation/openexr"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.9"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.4.9"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-190", "CWE-787" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T15:09:05Z",
    "nvd_published_at" : "2026-04-06T16:16:36Z"
  }
}

CVSS V3

5.0 HIGH

Attack Vector Local (AV:L)

Attack Complexity Low (AC:L)

Privileges Required Low (PR:L)

User Interaction Required (UI:R)

Scope Unchanged (S:U)

Confidentiality None (C:N)

Integrity None (I:N)

Availability High (A:H)

Vector String

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Advisory Metadata

Source ID: GHSA-p8xc-w3q4-h64x
Schema Version: 1.4.0
Published: 2026-04-08 15:09
Last Modified: 2026-04-08 15:09
Database Record File: advisories/github-reviewed/2026/04/GHSA-p8xc-w3q4-h64x/GHSA-p8xc-w3q4-h64x.json