Sumatrapdf
CVE-2026-23951
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK
1 technique across 1 tactic: Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS 5.5 (MEDIUM). Attack vector: Local. Complexity: Low. Privileges required: None. User interaction: Required. Public exploit/POC available. |
| Exploit ScenarioDerived | An attacker could exploit this flaw, an out-of-bounds heap read that crashes the app. |
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Alert meAnalysisAIv1 – Mar 12, 2026
SumatraPDF on Windows is vulnerable to a denial-of-service attack through a maliciously crafted Mobi file that triggers an integer underflow in record validation, causing an out-of-bounds heap read and application crash. The vulnerability stems from an off-by-one error in the PalmDbReader::GetRecord function that only occurs with exactly 2 records, and public exploit code is available. No patch has been released at this time.
Earlier versions of this analysis (1)
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. [CVSS 5.5 MEDIUM]
RemediationAI
Monitor vendor advisories for a patch.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-125 (Out-of-bounds Read). Affects Sumatrapdf. 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.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
Lifecycle Timeline
2DescriptionGitHub Advisory
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.
Executive ViewAI
Organizations using SumatraPDF should be aware of moderate risk from CVE-2026-23951, a out-of-bounds read vulnerability rated CVSS 5.5. Exploitation could cause memory corruption or application crashes. Proof-of-concept code is publicly available. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: enable ASLR/DEP, apply network segmentation.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Integer overflow occurs when an arithmetic operation produces a result that exceeds the maximum value a given integer type can store.
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
Affected Products (CPE)GitHub Advisory
More in Sumatrapdf
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SumatraPDF 3.5.2 and earlier on Windows allows arbitrary code execution when a user opens a PDF and selects "Show in fol
SumatraPDF versions 3.5.0 through 3.5.2 fail to validate TLS certificates during software updates and execute installers
Heap-based buffer overflow in SumatraPDF before 2.1 allows remote attackers to execute arbitrary code via a crafted PDF
Heap-based buffer overflow in SumatraPDF before 2.1 allows remote attackers to execute arbitrary code via a crafted PDF
SumatraPDF versions 3.5.2 and earlier are vulnerable to a heap buffer over-read in the MOBI file parser due to incomplet
A buffer overflow in SumatraPDF Reader v3.4.6 allows attackers to cause a Denial of Service (DoS) via a crafted text fil
Local code execution in SumatraPDF 3.6.1 and earlier on Windows is possible when a user opens an attacker-supplied docum
Parsing a malformed PDF in SumatraPDF 3.6.1 can crash the reader through a signed integer overflow in the PageLabels han
Command-line argument injection in SumatraPDF 3.5.2 and earlier lets an attacker-controlled SyncTeX source filename esca
Argument injection in the AI translation feature of SumatraPDF 3.6.1 and earlier allows text placed in a document select
Opening a crafted MOBI e-book in SumatraPDF versions before 3.6 can crash the application because the MOBI header decode
Exploit-DB