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CVE-2026-107731: SumatraPDF: LIT parser range-validation flaws cause invalid-pointer reads and denial of service

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-09
• Weakness: CWE-125

Description

SumatraPDF is a multi-format reader for Windows. In 3.7.0.22298, four independently reachable range-validation variants in src/LitDoc.cpp allow file-controlled offsets and sizes to overflow, narrow to negative values, or wrap before incomplete bounds checks. The affected calculations include contentOffset, the directory expression dirOff64 + dirLen64, and the decoded-section offset + size, along with secondary-header range handling. Opening a crafted LIT file that reaches one of these variants can cause invalid pointer reads and deterministic application termination. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.

Affected products

• sumatrapdfreader sumatrapdf: through 3.7.0.22298

References

• https://github.com/sumatrapdfreader/sumatrapdf/commit/5d43b8cf9c45335ffd47e616bfa27648f17d0b63
• https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-753j-hx3p-xm9g

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