How severe is CVE-2019-18426?

CVE-2019-18426 has a CVSS score of 8.2/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2019-18426?

Affected package information for CVE-2019-18426 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2019-18426?

No fixed release is recorded for CVE-2019-18426 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2019-18426 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2019-18426 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2019-18426 actively exploited in the wild?

Yes. There are 8 known exploit references for CVE-2019-18426, including 1 documented proof-of-concept exploit on Exploit-DB and 6 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2019-18426?

CVE-2019-18426 has an EPSS (Exploit Prediction Scoring System) score of 67.9%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2019-18426 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2019-18426 (WhatsApp Cross-Site Scripting Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-05-23. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-06-13. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2019-18426?

CVE-2019-18426 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2019-18426 published, and has it been updated?

CVE-2019-18426 was published on January 21, 2020 and was last updated on October 21, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🛡️

CISA KEV · ACTIVELY EXPLOITED

HIGH severity

CVE-2019-18426

HIGH

CVE-2019-18426 is a high-severity (CVSS 8.2) Cross-site Scripting (XSS) vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-05-23) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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…

Published

Jan 21, 2020

Updated

Oct 21, 2025

Affected

1 product

Patched

See advisory

Exploits

8 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-05-23. Federal agencies were required to remediate by 2022-06-13.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2019-18426.

EPSS Exploitation Probability

via FIRST.org ↗

67.9%probability of exploitation in next 30 days

High Risk0.00%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2019-18426 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

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 Products

1 product · 2 configurations

Application

whatsappwhatsapp

< 2.20.10

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-48295webappsmultiple

WhatsApp Desktop 0.3.9308 - Persistent Cross-Site Scripting

by Gal Weizman · Apr 6, 2020

Exploit-DB Source

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2019-18426 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2019-18426 in your dependencies?

Find it across , including transitive dependencies.

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CVSS Score

8.2/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No known public exploit tooling found.

Timeline

Disclosed

Jan 21, 2020

First exploit

Apr 6, 2020

KEV added

May 23, 2022

Last updated

Oct 21, 2025

Identifiers

CVE-2019-18426

References

Webfacebook.com Webpacketstormsecurity.com Webcisa.gov

Related vulnerabilities

This CVE is high severity; 1 of 8 other CVEs with CWE-79 is rated as high or higher (top: critical).

CVE-2026-114061GHSA-2rqm-h6hv-g79vCVE-2026-115897CVE-2026-114128CVE-2026-63430GHSA-c6gr-qvv4-5v3fGHSA-cg2g-xh64-v4q7CVE-2026-114130Browse all CWE-79

Provenance

Sources

OSV.devNVDCISA KEVFIRST.org (EPSS)

Last verifiedOct 21, 2025