TI-2026-69818 Aliases CVE-2026-107738

Out-of-bounds read in SumatraPDF CHM parser crashes the application

LOW 29CWE-125Published 2026-10-08 · Updated 2026-10-14

Key facts

Attack vector: Local
Privileges required: None
User interaction: Passive
Attack complexity: Low
Attack requirements: None
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-125 and the CVSS impact.

Summary

SumatraPDF 3.6.1 and earlier, a multi-format reader for Windows, is affected. In ChmFile::GetCharZ(), unsigned string offsets read from the /#WINDOWS and /#IVB sections are converted to signed integers without a lower-bound check (CWE-125). An attacker can get a user to open a crafted file. A negative offset then makes the function read memory before the /#STRINGS buffer, which terminates the application.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, ChmFile::GetCharZ() narrows file-controlled unsigned string offsets from /#WINDOWS and /#IVB to signed integers without a lower-bound check. An offset that becomes negative can make the function read before the /#STRINGS buffer, causing deterministic application termination. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.0012 1st percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
sumatrapdfreader	sumatrapdf	up to 3.6.1	—	No fix listed	CNA

sumatrapdf Vendorsumatrapdfreader Affected up to 3.6.1 Fixed in — No fix listed CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:sumatrapdfreader:sumatrapdf::::::::	—	—	sumatrapdfreader

cpe:2.3:a:sumatrapdfreader:sumatrapdf:*:*:*:*:*:*:*:* Versions — — ·sumatrapdfreader

Remediation

The sources list no fixed version as of this review.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Timeline

2026-10-09 Threatist record created from CVE-2026-107738
2026-10-10 Priority changed: MEDIUM → LOW
2026-10-14 CISA SSVC decision points changed

References

Other 2

TI-2026-18936 SumatraPDF has an Untrusted Search Path in sumatrapdf/src/AppTools.cpp CVSS 3.1HIGH 8.6
TI-2025-35489 A null pointer dereference vulnerability was discovered in SumatraPDF 3.5.2 during the… CVSS 3.1HIGH 7.3
TI-2012-04514 SumatraPDF 2.1.1/MuPDF 1.0 allows remote attackers to cause an Integer Overflow in the… CVSS 3.1HIGH 7.8
TI-2026-69819 Argument injection in SumatraPDF selection translation on Windows CVSS 4.0HIGH 7.1
TI-2026-69814 SumatraPDF: SyncTeX Argument Injection in Inverse Search Enables Arbitrary Command Execution via External Editors CVSS 4.0HIGH 7.1
TI-2026-69813 Null pointer dereference in SumatraPDF CmdExec crashes the reader CVSS 4.0MEDIUM 6.8

See all 26 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences