CVE-2026-23951

SumatraPDF's Integer Underflow in PalmDbReader Leads to Crash

MEDIUM
5.5
CVSS Score
Published: January 22, 2026 at 12:17 AM UTC
Updated: June 17, 2026 at 10:22 AM UTC
1 product affected across 1 vendorSumatrapdf

Using sumatrapdf by sumatrapdfreader?

Get instant alerts when new vulnerabilities affect sumatrapdf - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
MEDIUM5.5
Exploit prediction
EPSS 0.2%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.5MEDIUMGitHub_M
Attack Vector
LOCAL
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-125CWE-191CWE-193

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card