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CVE-2026-86853

Repeated external URL scheme launches could potentially cause a denial of service in Firefox for iOS

MEDIUM
4.3
CVSS Score
Published: September 8, 2026 at 03:14 PM UTC
Updated: October 5, 2026 at 05:09 PM UTC
1 product affected across 1 vendorFirefox Mobile

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Severity
MEDIUM4.3
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Permissions Required
Source: cverecord
https://bugzilla.mozilla.org/show_bug.cgi?id=1847631
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-89/

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.3MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Vector?

Quick Info

StatusANALYZED
CWE
CWE-451

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