Vulnerability-Lookup

GHSA-P8XC-W3Q4-H64X

Vulnerability from github – Published: 2026-04-08 15:09 – Updated: 2026-04-08 15:09

Summary

OpenEXR: DWA Lossy Decoder Heap Out-of-Bounds Write

Details

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:

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:

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

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

Severity ?

5.0 (Medium)


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

8.4 (High)


                  
                    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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "OpenEXR"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.2.0"
            },
            {
              "fixed": "3.2.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "OpenEXR"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.3.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "OpenEXR"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.4.0"
            },
            {
              "fixed": "3.4.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34589"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-190",
      "CWE-787"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-08T15:09:05Z",
    "nvd_published_at": "2026-04-06T16:16:36Z",
    "severity": "HIGH"
  },
  "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 \u003c 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  -\u003e exr_decoding_run(...)\n     -\u003e exr_uncompress_chunk(...)\n        -\u003e internal_exr_undo_dwaa(...)\n           -\u003e DwaCompressor_uncompress(...)\n              -\u003e 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\u276f ./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 \u0027int\u0027\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\u0026, 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\u003cImf_4_0::InputPart\u003e /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\u003cchar const*\u003e /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",
  "id": "GHSA-p8xc-w3q4-h64x",
  "modified": "2026-04-08T15:09:05Z",
  "published": "2026-04-08T15:09:05Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "OpenEXR: DWA Lossy Decoder Heap Out-of-Bounds Write"
}

CVE-2026-34589 (GCVE-0-2026-34589)

Vulnerability from cvelistv5 – Published: 2026-04-06 15:33 – Updated: 2026-04-07 13:05

Title

OpenEXR: DWA Lossy Decoder Heap Out-of-Bounds Write

Summary

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, 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 vulnerability is fixed in 3.2.7, 3.3.9, and 3.4.9.

Severity ?

8.4 (High)


                        
                          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

CWE

CWE-190 - Integer Overflow or Wraparound
CWE-787 - Out-of-bounds Write

Assigner

GitHub_M

References

URL

Tags

	https://github.com/AcademySoftwareFoundation/open…	x_refsource_CONFIRM
	https://github.com/AcademySoftwareFoundation/open…	x_refsource_MISC
	https://github.com/AcademySoftwareFoundation/open…	x_refsource_MISC
	https://github.com/AcademySoftwareFoundation/open…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	AcademySoftwareFoundation	openexr	Affected: >= 3.2.0, < 3.2.7 Affected: >= 3.3.0, < 3.3.9 Affected: >= 3.4.0, < 3.4.9

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-34589",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-07T03:56:05.730658Z",
                "version": "2.0.3"
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "openexr",
          "vendor": "AcademySoftwareFoundation",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.2.0, \u003c 3.2.7"
            },
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              "status": "affected",
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        {
          "lang": "en",
          "value": "OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, 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 vulnerability is fixed in 3.2.7, 3.3.9, and 3.4.9."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
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            "attackVector": "LOCAL",
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "ACTIVE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
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              "lang": "en",
              "type": "CWE"
            }
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        },
        {
          "descriptions": [
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              "cweId": "CWE-787",
              "description": "CWE-787: Out-of-bounds Write",
              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-04-07T03:08:13.554Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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          "tags": [
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        },
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          "url": "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7"
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        }
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      "source": {
        "advisory": "GHSA-p8xc-w3q4-h64x",
        "discovery": "UNKNOWN"
      },
      "title": "OpenEXR: DWA Lossy Decoder Heap Out-of-Bounds Write"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-34589",
    "datePublished": "2026-04-06T15:33:03.276Z",
    "dateReserved": "2026-03-30T17:15:52.498Z",
    "dateUpdated": "2026-04-07T13:05:41.117Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-P8XC-W3Q4-H64X

Summary

Root Cause and Data Flow

Reproduction

CVE-2026-34589 (GCVE-0-2026-34589)

Tags

Sightings

Nomenclature