How severe is CVE-2026-86853?

CVE-2026-86853 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-86853 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-86853?

CVE-2026-86853 affects Mozilla Firefox Mobile. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-86853?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-86853 published?

CVE-2026-86853 was published on 2026-09-08 and last updated on 2026-10-05.

CVE-2026-86853

CVE-2026-86853 is a medium-severity vulnerability in Mozilla Firefox Mobile with a CVSS 3.x base score of 4.3. 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-451.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-451
Affected product: Mozilla Firefox Mobile
Published: 2026-09-08
Last modified: 2026-10-05

Description

A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external application launches. This could make Firefox for iOS temporarily unusable until the page is closed. This vulnerability was fixed in Firefox for iOS 155.1.

Frequently asked questions

What is CVE-2026-86853?: A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external application launches. This could make Firefox for iOS temporarily unusable until the page is closed. This vulnerability was fixed in Firefox for iOS 155.1.
How severe is CVE-2026-86853?: CVE-2026-86853 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-86853 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-86853?: CVE-2026-86853 affects Mozilla Firefox Mobile. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-86853?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-86853 published?: CVE-2026-86853 was published on 2026-09-08 and last updated on 2026-10-05.

References

Affected products (1)

cpe:2.3:a:mozilla:firefox_mobile:*:*:*:*:*:iphone_os:*:*

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