CVE-2026-16389: mozilla firefox Integer Overflow or Wraparound

Vulnerability summary

CVE-2026-16389 is a critical (CVSS 9.8) Integer Overflow or Wraparound vulnerability in mozilla firefox. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 46.1% of scored vulnerabilities.

Timeline

1. 21-07-2026
   PublishedVulnerability first disclosed.
2. 10-08-2026
   Last modifiedVulnerability information updated.

Description

Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

• CWE-190Integer Overflow or WraparoundThe product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.