CVE-2026-16396: Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

highCVSS 8.8CVE-2026-16396

Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: high — CVSS 8.8
Published: 2026-07-21
Last updated: 2026-07-24
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-16396

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-163960.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-16396	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[NEW] [high] Mozilla Firefox and Firefox ESR: Multiple vulnerabilitiescert-bund
unknownMultiple vulnerabilities in Mozilla Thunderbird (July 23, 2026)cert-fr-avis
unknownMozilla Products Multiple Vulnerabilitieshkcert
unknownMultiple vulnerabilities in Mozilla products (July 22, 2026)cert-fr-avis
unknownDSA-6394-1 firefox-esr - security updatedebian

Recent advisories for Privilege escalation in

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-16635: The Pronamic Pay plugin for WordPress is vulnerable to Privilege Escalation in all versions up…nvd · 2026-08-01
highCVE-2026-15414: The Subscriptions for WooCommerce plugin for WordPress is vulnerable to Privilege Escalation i…nvd · 2026-08-01
unknownCVE-2026-51953: An issue in FeehiCMS v.2.1.1 allows an attacker to escalate privileges via the Session managem…nvd · 2026-07-31
mediumGHSA-jr6p-8pjj-mfx6: Capsule has an incomplete fix of CVE-2026-22872: TenantResource RawItems and Generators s…ghsa · 2026-07-31
high[UPDATE] [high] PackageKit: Vulnerability allows privilege escalationcert-bund · 2026-07-31
high[UPDATE] [high] Linux Kernel: Multiple vulnerabilities allow denial of service and privilege escalationcert-bund · 2026-07-31