PatchTheCVECVE-2026-86853: A malicious webpage could repeatedly trigger external URL schemes, causing system prompts or external applicat
CVE-2026-86853 is a medium-severity flaw (CVSS 4.3) affecting firefox mobile. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 4.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.3% (top 80%) |
| CISA exploited list | No |
| Weakness | CWE-451 |
| Published | 2026-09-08 |
| Last modified | 2026-10-05 |
Last updated 2026-10-05 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-86853?
firefox mobile: upgrade to 155.1. Exact commands for each OS are on this page.
Is CVE-2026-86853 being exploited?
CVE-2026-86853 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-86853 affect?
CVE-2026-86853 affects firefox mobile. Severity is medium (CVSS 4.3). 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 Firef
How urgent is CVE-2026-86853?
Priority 20/100. No elevated risk signals yet.
Software pages
iOS vulnerabilities · Mozilla Firefox vulnerabilities
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