Firefox WebExtensions Privilege Escalation Fixed in v153 & ESR 140.13
CVE-2026-16396 Published on July 21, 2026

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

NVD

Vulnerability Analysis

CVE-2026-16396 is exploitable with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
REQUIRED
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Type

Improper Privilege Management

The software does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.


Products Associated with CVE-2026-16396

stack.watch emails you whenever new vulnerabilities are published in Mozilla Firefox or Mozilla Thunderbird. Just hit a watch button to start following.

Mozilla Firefox
 
Mozilla Thunderbird
 

Affected Versions

Mozilla Firefox: Mozilla Thunderbird:

Exploit Probability

EPSS
0.24%
Percentile
15.32%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.