How severe is CVE-2026-34588?

No CVSS score has been assigned to CVE-2026-34588 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34588?

CVE-2026-34588 affects the following packages: openexr (PyPI), openexr (PyPI), openexr (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-34588?

Update openexr to 3.2.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34588 is resolved across your whole dependency graph.

How do I detect CVE-2026-34588 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openexr, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34588 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2026-34588 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34588 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34588?

CVE-2026-34588 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 43th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34588?

CVE-2026-34588 is classified as Out-of-bounds Read (CWE-125), CWE-190 (CWE-190), Out-of-bounds Write (CWE-787). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34588 published, and has it been updated?

CVE-2026-34588 was published on April 6, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-34588 — openexr

CVE-2026-34588 is a Out-of-bounds Read vulnerability in openexr. A fix is available for openexr — see the affected versions and patch details below.

OpenEXR has a signed 32-bit Overflow in PIZ Decoder Leads to OOB Read/Write

Also known asGHSA-588r-cr5c-w6hfPYSEC-2026-2845

Published

Apr 6, 2026

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34588.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

3 pkgs affected

🐍openexr🐍openexr🐍openexr

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

internal_exr_undo_piz() advances the working wavelet pointer with signed 32-bit arithmetic:

wavbuf += nx * ny * wcount;

Because nx, ny, and wcount are int, a crafted EXR file can make this product overflow and wrap. The next channel then decodes from an incorrect address. The wavelet decode path operates in place, so this yields both out-of-bounds reads and out-of-bounds writes.

Tested on commit 7820b7e1b93405ba1d551c43a945018226b75bc5

Technical Details

The vulnerable decode path is:

internal_exr_undo_piz() sets wavbuf = decode->scratch_buffer_1.
For each channel, it calls wav_2D_decode (wavbuf + j, ...).
It then advances wavbuf with wavbuf += nx * ny * wcount.

The overflow happens in step 3. Once wavbuf is wrapped, the next channel's wavelet decode runs on the wrong address.

In the 14-bit wavelet path, wdec14_4() first reads:

*px
*p10
*p01
*p11

and then writes back to the same locations:

*px = ...
*p01 = ...
*p10 = ...
*p11 = ...

As a result, the bug is not just a crash-only invalid read. It is an out-of-bounds read/write condition.

Reproduction

piz_scanline_redzone.zip

Build exrcheck with ASAN and run:

❯ ./build-asan/bin/exrcheck /tmp/piz_scanline_redzone.exr
 file /tmp/piz_scanline_redzone.exr /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:373:19: runtime error: signed integer overflow: 134217724 * 32 cannot be represented in type 'int'
=================================================================
==1711239==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7bedc3934700 at pc 0x7bf1f100f498 bp 0x7ffe032d8f00 sp 0x7ffe032d8ef0
READ of size 2 at 0x7bedc3934700 thread T0
    #0 0x7bf1f100f497 in wdec14_4 /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:148
    #1 0x7bf1f100f497 in wav_2D_decode /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:403
    #2 0x7bf1f100f497 in internal_exr_undo_piz /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:727
    #3 0x7bf1f115b038 in exr_uncompress_chunk /home/pop/sec/openexr/src/lib/OpenEXRCore/compression.c:546
    #4 0x7bf1f1161168 in exr_decoding_run /home/pop/sec/openexr/src/lib/OpenEXRCore/decoding.c:580
    #5 0x7bf1f2a71add in run_decode /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:586
    #6 0x7bf1f2a83dc4 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 0x7bf1f28c6a81 in Imf_4_0::InputFile::Data::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfInputFile.cpp:458
    #8 0x7bf1f3bfe2dc in readScanline<Imf_4_0::InputPart> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:239
    #9 0x7bf1f3c05b04 in readMultiPart /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:905
    #10 0x7bf1f3c126fd in runChecks<char const*> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1171
    #11 0x7bf1f3c146b9 in Imf_4_0::checkOpenEXRFile(char const*, bool, bool, bool) /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1835
    #12 0x5d9675fce8f8 in exrCheck(char const*, bool, bool, bool, bool) /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:96
    #13 0x5d9675fcb2b1 in main /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:164
    #14 0x7bf1efe2a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #15 0x7bf1efe2a28a in __libc_start_main_impl ../csu/libc-start.c:360
    #16 0x5d9675fcc844 in _start (/home/pop/sec/openexr/build-asan/bin/exrcheck+0xe844) (BuildId: 087c972343a5372940c42c0a2e7bce4a84288aec)

0x7bedc3934700 is located 256 bytes before 8590720784-byte region [0x7bedc3934800,0x7befc39f4710)
allocated by thread T0 here:
    #0 0x7bf1f40fd9c7 in malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:69
    #1 0x7bf1f115883e in internal_decode_alloc_buffer /home/pop/sec/openexr/src/lib/OpenEXRCore/coding.c:256
    #2 0x7bf1f100da97 in internal_exr_undo_piz /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:643
    #3 0x7bf1f115b038 in exr_uncompress_chunk /home/pop/sec/openexr/src/lib/OpenEXRCore/compression.c:546
    #4 0x7bf1f1161168 in exr_decoding_run /home/pop/sec/openexr/src/lib/OpenEXRCore/decoding.c:580
    #5 0x7bf1f2a71add in run_decode /home/pop/sec/openexr/src/lib/OpenEXR/ImfScanLineInputFile.cpp:586
    #6 0x7bf1f2a83dc4 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 0x7bf1f28c6a81 in Imf_4_0::InputFile::Data::readPixels(int, int) /home/pop/sec/openexr/src/lib/OpenEXR/ImfInputFile.cpp:458
    #8 0x7bf1f3bfe2dc in readScanline<Imf_4_0::InputPart> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:239
    #9 0x7bf1f3c05b04 in readMultiPart /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:905
    #10 0x7bf1f3c126fd in runChecks<char const*> /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1171
    #11 0x7bf1f3c146b9 in Imf_4_0::checkOpenEXRFile(char const*, bool, bool, bool) /home/pop/sec/openexr/src/lib/OpenEXRUtil/ImfCheckFile.cpp:1835
    #12 0x5d9675fce8f8 in exrCheck(char const*, bool, bool, bool, bool) /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:96
    #13 0x5d9675fcb2b1 in main /home/pop/sec/openexr/src/bin/exrcheck/main.cpp:164
    #14 0x7bf1efe2a1c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #15 0x7bf1efe2a28a in __libc_start_main_impl ../csu/libc-start.c:360
    #16 0x5d9675fcc844 in _start (/home/pop/sec/openexr/build-asan/bin/exrcheck+0xe844) (BuildId: 087c972343a5372940c42c0a2e7bce4a84288aec)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/pop/sec/openexr/src/lib/OpenEXRCore/internal_piz.c:148 in wdec14_4
Shadow bytes around the buggy address:
  0x7bedc3934480: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934500: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934580: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934600: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934680: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x7bedc3934700:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934780: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bedc3934800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bedc3934880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bedc3934900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bedc3934980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
==1711239==ABORTING

To prove this is both READ and WRITE, we can also memcheck against non-ASAN release build:

valgrind --tool=memcheck --leak-check=no --track-origins=no \
  --error-limit=no --num-callers=20 \
  ./build-relwithdebinfo/bin/exrcheck /tmp/piz_scanline_redzone.exr

Observed result:

Invalid read of size 2 at internal_piz.c:150
Invalid write of size 2 at internal_piz.c:171

This confirms the bug is an OOB read/write, not only a read-first crash.

Redzone-Oriented File

width: 67108862
height: 32
channel A: FLOAT, sampling 1 x 1
channel B: HALF, sampling 33554431 x 16

This makes:

width * 32 * 2 = 4294967168

which wraps signed 32-bit arithmetic to -128.

That places the next wavbuf access just before the allocated buffer, producing a clean heap-overflow report.

Impact

A crafted EXR file can trigger out-of-bounds memory access during PIZ decompression. The primitive includes both invalid reads and invalid writes. Depending on allocator layout and surrounding memory, this could lead to process crash, memory corruption, or potentially stronger exploitation outcomes.

Recommended Fix

compute channel span in 64-bit arithmetic
reject any overflow in nx * ny * wcount
validate cumulative per-channel decoded footprint against outsz before wavelet decode
fail decompression if channel-derived layout does not exactly fit the decompression buffer

Found by: Quang Luong of Calif.io

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`openexr`	≥ 3.1.0&&< 3.2.7	3.2.7`pip install --upgrade 'openexr==3.2.7'`
🐍PyPI	`openexr`	≥ 3.3.0&&< 3.3.9	3.3.9`pip install --upgrade 'openexr==3.3.9'`
🐍PyPI	`openexr`	≥ 3.4.0&&< 3.4.9	3.4.9`pip install --upgrade 'openexr==3.4.9'`

Affected Products

1 product · 3 configurations

Application

openexropenexr

≥ 3.4.0 && < 3.4.9

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openexr, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update openexr to 3.2.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34588 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-34588 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Enterprise Linux 10	`openexr-0:3.1.10-8.el10_1.2`	RHSA-2026:15888
Red Hat Enterprise Linux 10	`openexr-0:3.1.10-8.el10_2.2`	RHSA-2026:19146
Red Hat Enterprise Linux 10.0 Extended Update Support	`openexr-0:3.1.10-8.el10_0.2`	RHSA-2026:17656
Red Hat Enterprise Linux 9	`openexr-0:3.1.1-3.el9_7.2`	RHSA-2026:15887
Red Hat Enterprise Linux 9	`openexr-0:3.1.1-3.el9_8.2`	RHSA-2026:19359
Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions	`openexr-0:3.1.1-2.el9_0.3`	RHSA-2026:19587
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions	`openexr-0:3.1.1-2.el9_2.3`	RHSA-2026:17659
Red Hat Enterprise Linux 9.4 Extended Update Support	`openexr-0:3.1.1-2.el9_4.3`	RHSA-2026:17658

Frequently Asked Questions

## Summary `internal_exr_undo_piz()` advances the working wavelet pointer with signed 32-bit arithmetic: ```c wavbuf += nx * ny * wcount; ``` Because `nx`, `ny`, and `wcount` are `int`, a crafted EXR file can make this product overflow and wrap. The next channel then decodes from an incorrect address. The wavelet decode path operates in place, so this yields both out-of-bounds reads and out-of-bounds writes. Tested on commit 7820b7e1b93405ba1d551c43a945018226b75bc5 ## Technical Details The vulnerable decode path is: 1. `internal_exr_undo_piz()` sets `wavbuf = decode->scratch_buffer_1`.

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