sumatrapdfreader SumatraPDF up to 3.7.0.22298 MOBI File src/MobiDoc.cpp DecodeExthHeader hdrLen integer overflow

Summaryinfo

A vulnerability described as problematic has been identified in sumatrapdfreader SumatraPDF up to 3.7.0.22298. This issue affects the function DecodeExthHeader of the file src/MobiDoc.cpp of the component MOBI File Handler. Executing a manipulation of the argument hdrLen can lead to integer overflow. This vulnerability is tracked as CVE-2026-107729. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in sumatrapdfreader SumatraPDF up to 3.7.0.22298. It has been declared as problematic. This vulnerability affects the function DecodeExthHeader of the file src/MobiDoc.cpp of the component MOBI File Handler. The manipulation of the argument hdrLen with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect availability. CVE summarizes:

SumatraPDF is a multi-format reader for Windows. In 3.7.0.22298, src/MobiDoc.cpp narrows the untrusted unsigned mobiHdr.hdrLen field to a signed integer for validation; values above INT_MAX become negative and bypass the upper-bound check. When the EXTH flag is set, the original unsigned value is reused as a pointer offset, causing DecodeExthHeader() to read beyond the record buffer. Opening a crafted MOBI file can reliably terminate the application with a native access violation; no code execution, information disclosure, or integrity impact has been demonstrated. No fixed version is available as of this review.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-107729 since 10/08/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (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

• 3.7.0.22298

Website

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

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