Medium severity · published Jan 22, 2026
CVE-2026-23951
SumatraPDF's Integer Underflow in PalmDbReader Leads to Crash
5.5
CVSS
0.2%
EPSS
No
On KEV
Description
SumatraPDF is a multi-format reader for Windows. All versions contain an off-by-one error in the validation code that only triggers with exactly 2 records, causing an integer underflow in the size calculation. This bug exists in PalmDbReader::GetRecord when opening a crafted Mobi file, resulting in an out-of-bounds heap read that crashes the app. There are no published fixes at the time of publication.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SU
sumatrapdf · sumatrapdfreader
<= 3.5.2rel · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-23951
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-23951
Product
https://github.com/sumatrapdfreader/sumatrapdf/blob/master/src/PalmDbReader.cpp
Exploit
https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-hj4w-c5x8-p2hv
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