CVE-2019-18426
CVE-2019-18426 is a security flaw in Meta Platforms WhatsApp, Meta’s messaging app. Attackers can run code in the browser of someone using Meta Platforms WhatsApp and act as them. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 23 May 2022.[1]
Meta Platforms WhatsApp is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Fixed in version 0.3.9309 of WhatsApp Desktop.
Description
CISA calls it a cross-site scripting in Meta Platforms WhatsApp. In its words: “A vulnerability in WhatsApp Desktop when paired with WhatsApp for iPhone allows cross-site scripting and local file reading.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is cross-site scripting (CWE-79), in MITRE’s list of common software weaknesses.
It scores 8.2 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists one fixed version: everything before it is affected.[2]
| Product | Fixed in |
|---|---|
| WhatsApp Desktop | 0.3.9309 |
Every device with Meta Platforms WhatsApp needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 23 May 2022, 853 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 13 Jun 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 68%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Meta Platforms has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update Meta Platforms WhatsApp now.Install the latest update from Meta Platforms on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- Check you’re on 0.3.9309 or later.Fixed in version 0.3.9309 of WhatsApp Desktop. Anything older is what attackers are going after.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.2.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 68%.[4] |
See also
Other Meta Platforms WhatsApp flaws
- CVE-2025-55177: incorrect authorization ·
- CVE-2019-3568: VOIP stack buffer overflow ·
Other cross-site scripting flaws
- CVE-2026-42897, Microsoft: exchange server cross-site scripting ·
- CVE-2025-48700, Synacor Zimbra Collaboration Suite (ZCS): cross-site scripting ·
- CVE-2025-66376, Synacor Zimbra Collaboration Suite (ZCS): cross-site scripting ·
- CVE-2025-68461, Roundcube Webmail: cross-site scripting ·
- CVE-2021-26829, OpenPLC ScadaBR: cross-site scripting ·
Added the same day
- CVE-2022-20821, Cisco IOS XR: open port ·
- CVE-2021-30883, Apple devices: memory corruption ·
- CVE-2021-1048, Android Kernel: use-after-free ·
- CVE-2021-0920, Android Kernel: race condition ·
- CVE-2020-1027, Microsoft Windows: kernel privilege escalation ·
Every Meta Platforms flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “WhatsApp Cross-Site Scripting Vulnerability”. Known Exploited Vulnerabilities Catalog, added 23 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2019-18426 Detail”. National Vulnerability Database, published 21 Jan 2020.
- ^ Meta Platforms. Advisories and fixes: facebook.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.679, percentile 99.3, 31 Oct 2026.
- CVE Program. “CVE-2019-18426”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.