CVE-2026-107729: sumatrapdfreader sumatrapdf Out-of-bounds Read

Vulnerability summary

CVE-2026-107729 is a medium (CVSS 5.5) Out-of-bounds Read vulnerability in sumatrapdfreader sumatrapdf. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 3.4% of scored vulnerabilities.

Timeline

1. 08-10-2026
   PublishedVulnerability first disclosed.
2. 09-10-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.