Vulnerability · Published Oct 8, 2026 · Assigned by GitHub_M
CVE-2026-107737SumatraPDF CHM `its://` signed index causes an out-of-bounds object lookup
Medium 5.7
In plain English
A medium-severity security flaw in sumatrapdf from sumatrapdfreader. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| sumatrapdfreader | sumatrapdf | <= 3.6.1 |
Weakness: CWE-129 · Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N