Critical· 9.8official fix available
CVE-2026-16382
A critical flaw in Mozilla’s Service Workers lets attackers bypass security checks in the browser’s DOM, potentially allowing malicious code to run or data to be stolen.
publishedJul 21, 2026
last modifiedJul 24, 2026
sourcesNVD
severity · cvss
9.8
critical · how bad it is
exploitation · epss
<1%
31th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Aug 22, 2026
An official fix is available, so this entry is kept for 30 days and then removed automatically.
01
Who is affected
Mozilla Firefox and Thunderbird browsers, versions earlier than 153.
02
Real-world impact
An attacker could trick the browser into executing harmful scripts or accessing sensitive information without the user’s knowledge.
03
Why this severity
The CVSS score of 9.8 reflects that the flaw requires no authentication or user interaction, yet it compromises confidentiality, integrity, and availability of the user’s data and system.
04
What to do about it
official fix available
recommended steps
- 01Upgrade Firefox to version 153 or later.
- 02Upgrade Thunderbird to version 153 or later.
- 03Restart the browsers to apply the update.
NVD-referenced vendor advisory
05
Timeline
- Jul 21, 2026 · 12d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 23, 2026 · 10d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
- Jul 24, 2026 · 9d agoAdvisory updatedThe NVD record was last revised.
06
How it’s attacked
Attack vectorNetwork (remote)
Attack complexityLow
Privileges requiredNone
User interactionNone needed
ScopeUnchanged
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07
References & advisories
- bugzilla.mozilla.org/show_bug.cgipermissions required
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →