CVE-2026-23951: Sumatrapdfreader Sumatrapdf

Medium severity, CVSS 5.5. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Sumatrapdfreader Sumatrapdf: affected versions not specified

Published 2026-01-22. Last modified 2026-06-17.