CVE-2025-3859Public exploitNetwork attack vector

Address-bar spoofing via tail-elided long URLs

Published Apr 30, 2025 · Updated Apr 13, 2026

Address-bar spoofing in Mozilla Firefox Focus before 138 allows remote attackers to misrepresent a visited site via a crafted long URL. The URLBar display path showed a hostname in a field whose tail elision could conceal the registrable domain; the patch normalizes the host and truncates its head. A user must open the crafted URL, and the established consequence is a false site identity in the address bar rather than code execution.

CVSS severity6.1
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Address-bar spoofing in Mozilla Firefox Focus before 138 allows remote attackers to misrepresent a visited site via a crafted long URL. The URLBar display path showed a hostname in a field whose tail elision could conceal the registrable domain; the patch normalizes the host and truncates its head. A user must open the crafted URL, and the established consequence is a false site identity in the address bar rather than code execution.

The record

CVE
CVE-2025-3859
Published
Apr 30, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-601, CWE-451
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
CWE-451User Interface (UI) Misrepresentation of Critical Information

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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