SumatraPDF: Heap out-of-bounds read in MOBI header parser. (CVE-2026-26054) | HOL Guard CVE

Medium · CVSS 6.8CVE-2026-26054

SumatraPDF: Heap out-of-bounds read in MOBI header parser.

Answer in brief

CVE-2026-26054 records a Medium severity (CVSS 6.8) vulnerability in SumatraPDF: Heap out-of-bounds read in MOBI header parser.. The current sources do not mark it as known exploited. The current feed maps sumatrapdfreader/sumatrapdf (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 24, 2026Updated Sep 24, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 24, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.8
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps sumatrapdfreader/sumatrapdf (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
sumatrapdfreader/sumatrapdfgeneric	<3.6	3.6

Recommended response

Check inventory. Check lockfiles and deployed manifests for sumatrapdfreader/sumatrapdf.
Review the reported fix. Update sumatrapdfreader/sumatrapdf to 3.6 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.