CVE-2026-86853: Vulnerability in Mozilla Firefox for iOS
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.
AI Analysis
Technical Summary
This vulnerability allows a malicious webpage to repeatedly invoke external URL schemes on Firefox for iOS, leading to system prompts or external app launches. This behavior can cause a denial of service by making the browser temporarily unusable until the offending page is closed. Mozilla fixed this issue in Firefox for iOS version 155.1 as detailed in their security advisory MFSA 2026-89.
Potential Impact
The vulnerability causes a denial of service condition by making Firefox for iOS temporarily unusable due to repeated external URL scheme triggers. There is no indication of data compromise or persistent system impact. The overall impact is rated low by the vendor.
Mitigation Recommendations
Update Firefox for iOS to version 155.1 or later to remediate this vulnerability. The vendor advisory confirms the issue is fixed in this version. No additional mitigation is required once updated.
CVE-2026-86853: Vulnerability in Mozilla Firefox for iOS
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.
CVSS v3.1
Score 4.3medium
Affected software
pkg:github/mozilla-mobile/firefox-iosRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability allows a malicious webpage to repeatedly invoke external URL schemes on Firefox for iOS, leading to system prompts or external app launches. This behavior can cause a denial of service by making the browser temporarily unusable until the offending page is closed. Mozilla fixed this issue in Firefox for iOS version 155.1 as detailed in their security advisory MFSA 2026-89.
Potential Impact
The vulnerability causes a denial of service condition by making Firefox for iOS temporarily unusable due to repeated external URL scheme triggers. There is no indication of data compromise or persistent system impact. The overall impact is rated low by the vendor.
Mitigation Recommendations
Update Firefox for iOS to version 155.1 or later to remediate this vulnerability. The vendor advisory confirms the issue is fixed in this version. No additional mitigation is required once updated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-09-08T15:03:57.380Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-89/","vendor":"Mozilla"}]
Threat ID: 6aa029c1acd9273b49d8b6c3
Added to database: 09/08/2026, 15:29:05 UTC
Last enriched: 09/08/2026, 15:37:43 UTC
Last updated: 09/09/2026, 00:35:18 UTC
Views: 13
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