Vulnerability

CVE-2026-16399

High· 7.5CVSS7.5EPSS0%

.rules3/5

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Threat signal

75/100

High

Severity

high

CVSS

7.5

EPSS

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

7.5/ 10HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactNoneNo integrity impact.
Availability ImpactNoneNo availability impact.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

0.15%

probability of exploitation in next 30 days

higher than 4% of all CVEs

Low exploitation likelihood — defer if no other signals fire.

Vendor VEX

No VEX statements published for CVE-2026-16399. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCTrack

Total impact on non-trivial mission systems

exploitation: none
automatable: no
impact: total
mission: support

Lifecycle

2026-07-21Published
2026-10-24Last modified1 source

CVE-2026-16399

CVSS

EPSS

Vendor VEX

Lifecycle

References

CVE-2026-16399

CVSS

EPSS

Vendor VEX

Lifecycle

References