# CVE-2026-107731: SumatraPDF integer overflow in LIT parser range validation

Source: https://junglewise.ai/threats/cve-2026-107731-sumatrapdf-is-a-multi-format-reader-for-windows-in-3-7-0-22298  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-08. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-107731 · Severity: medium · CVSS 5.5 · Published 2026-10-08

SumatraPDF is a document reader for Windows that handles multiple file formats. A flaw in its newly added LIT file parser allows maliciously crafted .lit files to cause the application to crash. An attacker can trigger a denial of service by tricking a user into opening a poisoned file.

Technologies: [SumatraPDF](https://junglewise.ai/threats/technologies/sumatrapdf). Vendors: [SumatraPDF](https://junglewise.ai/threats/vendors/sumatrapdf).

## Quick answers

**Is CVE-2026-107731 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-107731 being exploited in the wild.

**How severe is CVE-2026-107731?** Medium severity, with a CVSS score of 5.5, published 8 October 2026.

**Which products and versions are affected?** SumatraPDF 3.7.0.22298.

**Is there a fix for CVE-2026-107731?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-107731 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-107731?** Check whether you run SumatraPDF at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The LIT parser in src/LitDoc.cpp contains four independently reachable integer overflow and range-validation flaws affecting offset and size calculations (contentOffset narrowing, dirOff64 + dirLen64 overflow, decoded-section offset + size, and secondary-header handling). File-controlled values can overflow or wrap before bounds checks, producing invalid pointer reads that crash the application with access violations (0xC0000005). The attack requires local file access and user interaction to open a crafted .lit file; no code execution or information disclosure occurs.

## Affected products

- SumatraPDF SumatraPDF 3.7.0.22298

## Timeline

- 2026-09-16: disclosed
- 2026-10-08: advisory

## References

- [https://github.com/sumatrapdfreader/sumatrapdf/commit/5d43b8cf9c45335ffd47e616bfa27648f17d0b63](https://github.com/sumatrapdfreader/sumatrapdf/commit/5d43b8cf9c45335ffd47e616bfa27648f17d0b63)
- [https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-753j-hx3p-xm9g](https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-753j-hx3p-xm9g)

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