FirefoxWeb browser · Mozilla
CVE-2025-9183
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 · uneditedSpoofing issue in the Address Bar component. This vulnerability was fixed in Firefox 142 and Firefox ESR 140.2.
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 · moderate confidenceA spoofing vulnerability in the Firefox Address Bar allows attackers to misrepresent the displayed URL, potentially tricking users into believing they're visiting a legitimate website when they're actually on a malicious site. This could facilitate phishing attacks by making the address bar show fake or misleading information.
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
< 140.2.0< 142.0CVSS 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
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
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 installed Firefox versionOpen Firefox and navigate to the address bar, type 'about:firefox' and press Enter. Alternatively, click the menu button (three horizontal lines) > Help > About Firefox. The version number will be displayed on the page.Affected if The displayed version is less than 140.2.0 or falls between 140.2.0 and 142.0 (excluding 142.0 itself)
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Confirm Firefox release channelOn the 'about:firefox' page, locate the 'Update channel' or 'Version' section to identify whether you are running Firefox Stable, Beta, or ESR.Affected if Running any channel below version 142.0 (or below 140.2.0 for ESR) makes the address bar vulnerable to spoofing
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Verify address bar behavior (optional manual check)Observe that the address bar displays the full URL being navigated to. Note that this CVE is a vulnerability in how Firefox renders URLs, so any instance of the affected versions is potentially vulnerable regardless of user settings.Affected if Any Firefox installation on version 140.2.0-stable and below, or any 141.x version below 142.0, is affected by this flaw
If your Firefox version is below 140.2.0 or is any version from 140.2.0 up to but not including 142.0, your address bar is vulnerable to URL spoofing attacks.
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 · scoped140.2.0142.0
Update Firefox to version 142 or later, or Firefox ESR to version 140.2 or later, to remediate this vulnerability.
Firefox 142 or Firefox ESR 140.2
- 1. Check current Firefox version by navigating to about:Firefox in the address bar
- 2. If running Firefox 141.x or earlier (non-ESR), upgrade to Firefox 142 or later
- 3. If running Firefox ESR, upgrade to Firefox ESR 140.2 or later
- 4. To update: Go to Menu > Help > About Firefox, or download the latest version from https://www.mozilla.org/firefox/
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-9183 — 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-2025-9183 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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