CVE-2026-23951

SumatraPDF's Integer Underflow in PalmDbReader Leads to Crash

CVSS 5.5 MEDIUMEPSS 0.2%CWE-125 CWE-191

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 5.5EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

22 Jan 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected products

sumatrapdfreader · sumatrapdf

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References

https://github.com/sumatrapdfreader/sumatrapdf/blob/master/src/PalmDbReader.cpp https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-hj4w-c5x8-p2hv