Vulnerability · Published Jul 21, 2026 · Assigned by mozilla
CVE-2026-16389Incorrect boundary conditions, integer overflow in the Libraries component in NSS
Critical 9.8
In plain English
A critical-severity integer overflow in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.6%top 49.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nss | 2:3.87.1-1+deb12u4 | DEBIAN-CVE-2026-16389 |
| Debian:13 | nss | 2:3.110-1+deb13u4 | DEBIAN-CVE-2026-16389 |
| Debian:14 | nss | 2:3.126-1 | DEBIAN-CVE-2026-16389 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-16389 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-16389 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-16389 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-16389 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-16389 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-16389 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | see references |
| Mozilla | Thunderbird | see references |
Weakness: CWE-190 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H