Off-by-One Error in SumatraPDF Affects Multi-Format Reader for Windows
CVE-2026-23951

5.5MEDIUM

Key Information:

Vendor

SumatraPDFreader

Status
SumatraPDF
Vendor
CVE Published:
22 January 2026

What is CVE-2026-23951?

SumatraPDF, a multi-format reader for Windows, contains a vulnerability stemming from an off-by-one error in its validation code. This issue triggers exclusively when processing exactly two records, leading to an integer underflow in size calculations. Specifically, this flaw is located within the PalmDbReader::GetRecord function when opening a specially crafted Mobi file. The error can result in an out-of-bounds heap read, causing the application to crash. As of now, there are no published fixes for this vulnerability.

Affected Version(s)

sumatrapdf <= 3.5.2rel

References

https://github.com/sumatrapdfreader/sumatrapdf/security/a...
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https://github.com/sumatrapdfreader/sumatrapdf/blob/maste...
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CVSS V3.1

Score:
5.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.