Medium severity · published Oct 8, 2026
CVE-2026-107737
SumatraPDF CHM `its://` signed index causes an out-of-bounds object lookup
5.7
CVSS
0.2%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 8% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SU
sumatrapdf · sumatrapdfreader
<= 3.6.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-107737
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-107737
x_refsource_CONFIRM
https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-8p34-f32f-7rmq
x_refsource_MISC
https://github.com/sumatrapdfreader/sumatrapdf/commit/596c7e26e983549a77a3a38cae1147ab73792929
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