---
id: CVE-2026-26054
title: SumatraPDF is a multi-format reader for Windows
summary: >-
  SumatraPDF is a multi-format reader for Windows. Prior to 3.6, the
  MobiDoc::ParseHeader function in src/MobiDoc.cpp validates a record using
  kMobiHeaderMinLen but DecodeMobiDocHeader constructs a decoder sized for
  kMobiHeaderLen without …
severity: medium
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'
cwe:
  - CWE-125
vendor: sumatrapdfreader
product: sumatrapdf
affected:
  - sumatrapdf < 3.6
published: '2026-09-24'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T17:17:04.673'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-26054'
references:
  - url: >-
      https://github.com/sumatrapdfreader/sumatrapdf/commit/24b9ce83383bbaa48b3efe00e4d30cccea126198
    label: security-advisories@github.com
  - url: 'https://github.com/sumatrapdfreader/sumatrapdf/issues/5318'
    label: security-advisories@github.com
  - url: 'https://github.com/sumatrapdfreader/sumatrapdf/releases/tag/3.6rel'
    label: security-advisories@github.com
  - url: >-
      https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-27p6-wrfp-pgm8
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-24T17:48:30.383Z'
epss: 0.00135
epssPercentile: 0.02402
---

## Overview

SumatraPDF is a multi-format reader for Windows. Prior to 3.6, the MobiDoc::ParseHeader function in src/MobiDoc.cpp validates a record using kMobiHeaderMinLen but DecodeMobiDocHeader constructs a decoder sized for kMobiHeaderLen without receiving the actual remaining buffer length. A malformed MOBI file can use an attacker-controlled header length to bypass optional-field early returns and cause the decoder to read beyond a short heap buffer. Opening the crafted document can crash SumatraPDF. This issue is fixed in version 3.6.

## Remediation

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