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CVE-2026-34757 medium CVSS 5.1

Use-After-Free in LIBPNG (CVE-2026-34757)

Summary

Vulnerability in LIBPNG (CVE-2026-34757). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.6.57 or later.

Original description

The description as published by the source.

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. From 1.0.9 to before 1.6.57, passing a pointer obtained from png_get_PLTE, png_get_tRNS, or png_get_hIST back into the corresponding setter on the same png_struct/png_info pair causes the setter to read from freed memory and copy its contents into the replacement buffer. The setter frees the internal buffer before copying from the caller-supplied pointer, which now dangles. The freed region may contain stale data (producing silently corrupted chunk metadata) or data from subsequent heap allocations (leaking unrelated heap contents into the chunk struct). This vulnerability is fixed in 1.6.57.

Source: NIST National Vulnerability Database NVD

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-2026-34757 has been found in LIBPNG.
Risk of unauthorized operations or information disclosure. CVSS score: 5.1/10.
What to do: upgrade LIBPNG to 1.6.57 or later.
If unsure, ask your IT team or search "LIBPNG CVE-2026-34757" on the vendor's site.

CVE-2026-34757 (LIBPNG) — CWE-416 / CVSS v3 5.1
Attack vector: local / unauthenticated / no user interaction
Patched: 1.6.57 — 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

Use-after-free (CWE-416) exists in LIBPNG.

📍 Affected scope

Check the vendor advisory for the affected versions of LIBPNG.

🔥 Severity

Severity: Medium (CVSS 5.1/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.6.57.

🛡️ 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 'LIBPNG' . 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 'LIBPNG' . | 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 LIBPNG 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 LIBPNG to 1.6.57

    ステージング環境で 1.6.57 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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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