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FirefoxWeb browser · Mozilla

CVE-2009-2953

MEDIUM · 5.0 CVSS v2.0 Published 2009-08-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
Mozilla Firefox 3.0.6 through 3.0.13, and 3.5.x, allows remote attackers to cause a denial of service (CPU consumption) via JavaScript code with a long string value for the hash property (aka location.hash), a related issue to CVE-2008-5715.

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 confidence

Mozilla Firefox versions 3.0.6 through 3.0.13 and 3.5.x contain a denial of service vulnerability where JavaScript code with an excessively long string value assigned to the location.hash property causes high CPU consumption, potentially rendering the browser unresponsive.

MitigationUpdate Firefox to a version beyond 3.0.13/3.5.x, or apply vendor-supplied patches. Users can also disable JavaScript or use add-ons like NoScript as a workaround.

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
Affected:= 3.0.6= 3.0.7= 3.0.8= 3.0.9= 3.0.10= 3.0.11= 3.0.12= 3.0.13= 3.5= 3.5.1= 3.5.2= 3.5.3

CVSS 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
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial

AV:N/AC:L/Au:N/C:N/I:N/A:P

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 checks

Work through these to decide whether this CVE applies to you.

  1. Determine Firefox version
    Open Firefox, click Help > About Mozilla Firefox, or navigate to about:support to see the version number
    Affected if The version is 3.0.6, 3.0.7, 3.0.8, 3.0.9, 3.0.10, 3.0.11, 3.0.12, 3.0.13, 3.5, 3.5.1, 3.5.2, or 3.5.3
  2. Verify JavaScript is enabled
    In Firefox address bar, type about:config and press Enter. Search for the javascript.enabled preference
    Affected if JavaScript is set to true (enabled)
  3. Confirm vulnerability trigger condition
    The vulnerability is triggered when JavaScript code assigns an excessively long string to the location.hash property. This is a browser behavior that can be tested with a simple JavaScript payload, but the primary condition is being on an affected version with JavaScript enabled
    Affected if Both conditions are met: affected Firefox version listed above AND JavaScript enabled

A user is affected if they are running Firefox version 3.0.6 through 3.0.13 or 3.5.x through 3.5.3 with JavaScript enabled, as this combination allows the long string location.hash DoS to trigger high CPU consumption.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update Firefox to a version beyond 3.0.13/3.5.x, or apply vendor-supplied patches. Users can also disable JavaScript or use add-ons like NoScript as a workaround.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2009-2953 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data