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Actively exploited

CVE-2019-18426 WhatsApp Cross-Site Scripting Vulnerability

A vulnerability in WhatsApp Desktop when paired with WhatsApp for iPhone allows cross-site scripting and local file reading.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 23 May 2022.
  • Rated High severity (CVSS 8.2, scored by CISA).
  • It has been in the catalogue for 1,628 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

A vulnerability in WhatsApp Desktop versions prior to 0.3.9309 when paired with WhatsApp for iPhone versions prior to 2.20.10 allows cross-site scripting and local file reading. Exploiting the vulnerability requires the victim to click a link preview from a specially crafted text message.

Affected Versions

ProductVersions
Facebook WhatsApp Desktop0.3.9309
unspecified to before 0.3.9309

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Meta Platforms WhatsApp. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 13 Jun 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Meta Platforms Flaws

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CVE-2025-55177Meta Platforms WhatsApp Incorrect Authorization VulnerabilityAdded 2 Sep 2025CVE-2019-3568WhatsApp VOIP Stack Buffer Overflow VulnerabilityAdded 19 Apr 2022

All 3 exploited Meta Platforms vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2019-18426
  3. CVE record: CVE-2019-18426
  4. FIRST EPSS
  5. facebook.com/security/advisories/cve-2019-18426
  6. packetstormsecurity.com/files/157097/WhatsApp-Desktop-0.3.9308-Cross-Site-Scripting.html