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VulnerabilityPublished

CVE-2026-42090: streetwriters notesnook · Cross-site Scripting

Affects streetwriters notesnookSource CVE Database V5

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Not known to be exploited · CVSS 9.6 Critical : upgrade to 3.3.15 as a priority.

Data as of 31 Oct 2026, 20:20 UTC

CVSS 3.1 base score
9.6Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.3.15
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 4 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

What to do

Upgrade streetwriters/notesnook to 3.3.15.

Affected software

ProductAffectedFixed in
streetwritersnotesnookAffected
  • =Notesnook Web/Desktop < 3.3.15
  • =Notesnook iOS/Android < 3.3.20
Fixed in–
GitHubstreetwriters/notesnookpkg:github/streetwriters/notesnookOther threatsAffected
  • <3.3.15
Fixed in
  • 3.3.15

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability has been patched in Notesnook Web/Desktop version 3.3.15 and Notesnook iOS/Android version 3.3.20. Users and administrators should upgrade to these or later versions to remediate the issue. Patch status is confirmed by the vendor advisory embedded in the description. No additional mitigations are indicated by the vendor.

Description

CVE-2026-42090 is a critical stored cross-site scripting (XSS) vulnerability in the Notesnook note-taking application affecting versions prior to 3.3.15 on Web/Desktop and prior to 3.3.20 on iOS/Android. The vulnerability arises because note fields such as title, headline, and content are inserted into an HTML template without proper HTML escaping during the note export flow. This allows malicious script injection that executes in a same-origin, unsandboxed iframe. In the desktop app, this escalates to remote code execution (RCE) due to Electron's insecure configuration (nodeIntegration: true, contextIsolation: false). The issue has been patched in the specified versions.

References

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