Medium severity · published Sep 24, 2026
CVE-2026-26054
SumatraPDF: Heap out-of-bounds read in MOBI header parser.
6.8
CVSS
0.2%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 11% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SU
sumatrapdf · sumatrapdfreader
< 3.6 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-26054
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-26054
x_refsource_CONFIRM
https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-27p6-wrfp-pgm8
x_refsource_MISC
https://github.com/sumatrapdfreader/sumatrapdf/issues/5318
x_refsource_MISC
https://github.com/sumatrapdfreader/sumatrapdf/commit/24b9ce83383bbaa48b3efe00e4d30cccea126198
x_refsource_MISC
https://github.com/sumatrapdfreader/sumatrapdf/releases/tag/3.6rel
More from sumatrapdf
8.4
CVE-2026-107732
SumatraPDF: Markup/command-link injection into UI notification text
7.8
CVE-2026-25880
Untrusted Search Path in SumatraPDF Reader (explorer.exe on Windows)
7.8
CVE-2026-23512
SumatraPDF has an Untrusted Search Path in sumatrapdf/src/AppTools.cpp
7.8
CVE-2012-5340
SumatraPDF 2.1.1/MuPDF 1.0 allows remote attackers to cause an Integer Overflow in the lex_number() function via a corrupt PDF file
7.8
CVE-2013-2830
Use-after-free vulnerability in SumatraPDF Reader 2.x before 2.2.1 allows remote attackers to execute arbitrary code via a crafted PDF file