FirefoxWeb browser · Mozilla
CVE-2026-13356
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA malicious webpage could interrupt a pending navigation by enqueuing a synchronous JavaScript dialog, causing the browser UI to display the destination origin in the address bar while continuing to render attacker-controlled content. This vulnerability was fixed in Firefox for iOS 152.3.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA race condition in Firefox for iOS allows a malicious page to interrupt pending navigation by triggering a synchronous JavaScript dialog. This causes the address bar to display the destination origin while attacker-controlled content continues to render, enabling URL spoofing/phishing attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FirefoxWeb browser
< 152.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Firefox for iOS version numberOpen the Firefox for iOS app, tap the menu (three lines) in the bottom-right, then tap Settings. Scroll to the bottom where the version number is displayed under 'Firefox' or 'About Firefox'.Affected if The displayed version is a number less than 152.3 (for example, 152.2, 152.1, 151.x, or earlier).
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Confirm via iOS SettingsOpen the iOS Settings app, scroll down to find Firefox in the app list, tap it, and check the Version field shown there.Affected if The version shown is less than 152.3.
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Verify JavaScript dialog behavior (optional confirmation)While the race condition is difficult to test directly, note that this vulnerability requires a malicious page to trigger a synchronous dialog (alert/confirm/prompt) during navigation. Any unexpected URL bar behavior during such events could indicate exploitation.Affected if You observe the address bar showing one origin while page content renders under a different origin after dismissing a synchronous JavaScript dialog during page navigation.
You are affected if Firefox for iOS version 152.3 or later is NOT installed on your device; the vulnerability exists in any version below 152.3.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped152.3
Users of Firefox for iOS should update to version 152.3 or later. Web application developers cannot directly fix this browser vulnerability but should educate users about browser updates and consider adding warnings about this attack vector in security documentation.
Firefox for iOS 152.3
- Upgrade Firefox for iOS to version 152.3 or later by opening the App Store, navigating to the Firefox app, and selecting the update option
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Testing1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-13356 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-13356 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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