---
id: CVE-2026-107738
title: SumatraPDF is a multi-format reader for Windows
summary: >-
  SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier,
  ChmFile::GetCharZ() narrows file-controlled unsigned string offsets from
  /#WINDOWS and /#IVB to signed integers without a lower-bound check. An offset
  that becomes ne…
severity: medium
cwe:
  - CWE-125
published: '2026-10-08'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T02:16:58.240'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107738'
references:
  - url: >-
      https://github.com/sumatrapdfreader/sumatrapdf/commit/62254ed6d781ceb5cd16489bb423e7f591cd72c4
    label: security-advisories@github.com
  - url: >-
      https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-33jg-vxm6-8mxx
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
epss: 0.0012
epssPercentile: 0.01806
ingestedAt: '2026-10-09T00:19:50.973Z'
vendor: sumatrapdfreader
product: sumatrapdf
affected:
  - sumatrapdf <= 3.6.1
cvss: 6.8
cvssVector: 'CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-14T01:35:46.846461Z'
cvssSource: cna
---

## Overview

SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, ChmFile::GetCharZ() narrows file-controlled unsigned string offsets from /#WINDOWS and /#IVB to signed integers without a lower-bound check. An offset that becomes negative can make the function read before the /#STRINGS buffer, causing deterministic application termination. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.