Buffer Overflow in SumatraPDF is a multi-format reader for Windows. In (CVE-2026-55586)
Summary
Vulnerability in SumatraPDF is a multi-format reader for Windows. In (CVE-2026-55586). Data can be tampered with by attackers.
Original description
The description as published by the source.
SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CHMLib/lzx.c. In the long-code branch, the function writes new internal nodes through next_symbol before validating that the canonical Huffman table has overflowed. The PRETREE case can write beyond the 104-entry PRETREE_table into adjacent heap state in struct LZXstate when reached through chm_open, chm_retrieve_object, LZXdecompress, and BUILD_TABLE. This produces heap memory corruption in the parser process, while arbitrary code execution has not been demonstrated. No fixed version is available as of this review.
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-2026-55586 has been found in SumatraPDF is a multi-format reader for Windows. In.
Data can be tampered with by attackers. CVSS score: 6.6/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "SumatraPDF is a multi-format reader for Windows. In CVE-2026-55586" on the vendor's site.
CVE-2026-55586 (SumatraPDF is a multi-format reader for Windows. In) — CWE-119 / CVSS v3 6.6
Attack vector: local / unauthenticated
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.
A vulnerability (CWE-119) exists in SumatraPDF is a multi-format reader for Windows. In.
Check the vendor advisory for the affected versions of SumatraPDF is a multi-format reader for Windows. In.
Severity: Medium (CVSS 6.6/10). Data can be tampered with by attackers.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで SumatraPDF is a multi-format reader for Windows. In を使っているサービスとバージョンを洗い出す。
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2Post-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。
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com