Medium severity · published Sep 8, 2026
CVE-2026-86853
Repeated external URL scheme launches could potentially cause a denial of service in Firefox for iOS
4.3
CVSS
0.3%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FM
Firefox Mobile · Mozilla
before 155.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86853
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86853
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=1847631
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-89/
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