How severe is CVE-2026-84135?

CVE-2026-84135 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-84135 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-84135?

CVE-2026-84135 affects Mozilla Firefox Mobile. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-84135?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-84135 published?

CVE-2026-84135 was published on 2026-09-01 and last updated on 2026-09-03.

CVE-2026-84135

CVE-2026-84135 is a critical-severity vulnerability in Mozilla Firefox Mobile with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Mozilla Firefox Mobile
Published: 2026-09-01
Last modified: 2026-09-03

Description

Other issue in Firefox Focus for Android. This vulnerability was fixed in Firefox 155.

Frequently asked questions

What is CVE-2026-84135?: Other issue in Firefox Focus for Android. This vulnerability was fixed in Firefox 155.
How severe is CVE-2026-84135?: CVE-2026-84135 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-84135 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-84135?: CVE-2026-84135 affects Mozilla Firefox Mobile. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-84135?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-84135 published?: CVE-2026-84135 was published on 2026-09-01 and last updated on 2026-09-03.

References

Affected products (1)

cpe:2.3:a:mozilla:firefox_mobile:*:*:*:*:*:android:*:*

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