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CVE-2026-107737

SumatraPDF CHM `its://` signed index causes an out-of-bounds object lookup

No known exploitation. EPSS puts it in the 8th percentile. No fix published yet.

CVSS —Not scoredEPSS percentile8th0.2% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFixNone yetNo fix or workaround published

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build or workaround is published yet. Limit exposure and watch for a patch.

  • Sumatrapdfreader SumatrapdfAffected: <= 3.6.1Upgrade to: not statedStated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS8th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.2% chance of exploitation activity in the next 30 days, which ranks it in the 8th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

4 events over 5 days, from the signal feeds we watch.

  1. Record updated
  2. Publishedweakness classified, record updated

Affected products

Technical detail

Weaknesses

Sources

References in the record

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