CVE-2026-107729
SumatraPDF: Unsigned-to-signed hdrLen validation bypass in SumatraPDF MOBI parsing causes out-of-bounds read
- State
- Published
- Severity
- 5.5 Medium
- Published
- Oct 8, 2026
- Updated
- Oct 9, 2026
- Reserved
- Oct 8, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.5 Medium | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | GitHub_M |
Weaknesses
- CWE-125 Out-of-bounds Read
Affected Products
| Product | Versions |
|---|---|
sumatrapdfsumatrapdfreader |
|
References
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