CVE-2025-4215Public exploitNetwork attack vector

Dashboard UI freeze via trailing-whitespace regex backtracking

Published May 2, 2025 · Updated Jun 12, 2025

Regular-expression denial of service in uBlock Origin 1.63.3b16 allows remote attackers to freeze the extension dashboard with crafted filter text. The getEditorText and setEditorText paths in the custom-filter editor apply the end-anchored /\s+$/ pattern to editor content, causing excessive backtracking on a long run of spaces followed by a nonspace. Successful triggering requires delivery of the crafted string to the custom-filter editor through a separate injection path; the demonstrated consequence is an unresponsive extension dashboard and browser UI.

CVSS severity3.7
Low
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular-expression denial of service in uBlock Origin 1.63.3b16 allows remote attackers to freeze the extension dashboard with crafted filter text. The getEditorText and setEditorText paths in the custom-filter editor apply the end-anchored /\s+$/ pattern to editor content, causing excessive backtracking on a long run of spaces followed by a nonspace. Successful triggering requires delivery of the crafted string to the custom-filter editor through a separate injection path; the demonstrated consequence is an unresponsive extension dashboard and browser UI.

The record

CVE
CVE-2025-4215
Published
May 2, 2025
Updated
Jun 12, 2025
Vendor
Raymond Hill
Product
uBlock Origin
Classifications
CWE-1333, CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 2, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.63.3b16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Raymond Hill · uBlock Originversion=1.63.3b16

Published CVSS scores

3.7NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
2.6VulDBAV:N/AC:H/Au:N/C:N/I:N/A:P
3.1VulDBCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
2.3VulDBCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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