CVE-2026-0889Public exploitNetwork attack vector

Browser crash via oversized Service Worker script

Published Jan 13, 2026 · Updated Jan 13, 2026

Denial of service in Mozilla Firefox before 147 allows remote attackers to crash the browser by serving an oversized Service Worker script. Service Worker registration accepts the oversized script before enforcing nsTString’s length limit, triggering a release assertion and process crash. Loading the attacker-controlled page is sufficient; testing reproduced a whole-browser crash on Windows and a segmentation fault on Linux without memory corruption.

CVSS severity7.5
High
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Mozilla Firefox before 147 allows remote attackers to crash the browser by serving an oversized Service Worker script. Service Worker registration accepts the oversized script before enforcing nsTString’s length limit, triggering a release assertion and process crash. Loading the attacker-controlled page is sufficient; testing reproduced a whole-browser crash on Windows and a segmentation fault on Linux without memory corruption.

The record

CVE
CVE-2026-0889
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 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?

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

  1. Affected versionversion=unspecified <147

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <147

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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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-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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