sumatrapdfreader SumatraPDF up to 3.6.1 IE fallback backend ParseProtoUrl/FindHtmlWindowById out-of-bounds

Summaryinfo

A vulnerability was found in sumatrapdfreader SumatraPDF up to 3.6.1. It has been classified as critical. Affected by this vulnerability is the function ParseProtoUrl/FindHtmlWindowById of the component IE fallback backend. The manipulation leads to out-of-bounds. This vulnerability is traded as CVE-2026-107737. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in sumatrapdfreader SumatraPDF up to 3.6.1 and classified as critical. This issue affects the function ParseProtoUrl/FindHtmlWindowById of the component IE fallback backend. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, and in pre-release 3.7.0.20369 when WebView2 is absent or cannot initialize, ParseProtoUrl() accepts the signed host component of an its:// URL and FindHtmlWindowById() uses it directly as an index into gHtmlWindows. Opening a crafted CHM through the IE fallback backend with a negative or otherwise out-of-range window identifier can cause an out-of-bounds pointer read followed by an invalid object callback dereference and process termination. No fixed version is available as of this review.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-107737 since 10/08/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/09/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• sumatrapdfreader

Name

• SumatraPDF

Version

• 3.6.0
• 3.6.1

Website

• Product: https://github.com/sumatrapdfreader/sumatrapdf/

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