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CVE-2026-34589 medium CVSS 5.0

Vulnerability in openexr (CVE-2026-34589)

Summary

Vulnerability in openexr (CVE-2026-34589). Risk of unauthorized operations or information disclosure. Exploitable via rowBlock. Mitigation: upgrade to 3.4.9 or later.

Original description

The description as published by the source.

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(.…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-34589 has been found in openexr.
Attackers can target a specific entry point like rowBlock over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.0/10.
What to do: upgrade openexr to 3.4.9 or later.
If unsure, ask your IT team or search "openexr CVE-2026-34589" on the vendor's site.

CVE-2026-34589 (openexr) — CWE-190 / CVSS v3 5.0
Attack vector: local
Attack surface: rowBlock / exrcheck / int / numBlocksX
Patched: 3.4.9 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-190) exists in openexr. Attackers reach the vulnerable code path via rowBlock.

📍 Affected scope

Check the vendor advisory for the affected versions of openexr. Attack surface: rowBlock / exrcheck / int / numBlocksX.

🔥 Severity

Severity: Medium (CVSS 5.0/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.4.9.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'openexr' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'openexr' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で openexr を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade openexr to 3.4.9

    ステージング環境で 3.4.9 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

PyPI openexr
[{"type":"ECOSYSTEM","events":[{"introduced":"3.4.0"},{"fixed":"3.4.9"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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