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FirefoxWeb browser · Mozilla

CVE-2012-3995

HIGH · 9.3 CVSS v2.0 Published 2012-10-10
Fix available
A fix is available. Upgrade to 10.0.8 / 16.0 or later.
See remediation →
100/100
Remediation priority · Urgent
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
The IsCSSWordSpacingSpace function in Mozilla Firefox before 16.0, Firefox ESR 10.x before 10.0.8, Thunderbird before 16.0, Thunderbird ESR 10.x before 10.0.8, and SeaMonkey before 2.13 allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read) via unspecified vectors.

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

Out-of-bounds read vulnerability in the IsCSSWordSpacingSpace CSS parsing function in Firefox, Thunderbird, and SeaMonkey allows remote attackers to execute arbitrary code or cause denial of service via unspecified vectors.

MitigationUpgrade to Firefox 16.0+, Firefox ESR 10.0.8+, Thunderbird 16.0+, Thunderbird ESR 10.0.8+, or SeaMonkey 2.13+ to patch the vulnerability.

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:< 10.0.8< 16.0
Ubuntu LinuxOperating system
Affected:= 10.04= 11.04= 11.10= 12.04
Enterprise Linux DesktopOperating system
Affected:= 5.0= 6.0
Enterprise Linux EusOperating system
Affected:= 6.3
Enterprise Linux ServerOperating system
Affected:= 5.0= 6.0
Enterprise Linux WorkstationOperating system
Affected:= 5.0= 6.0
Thunderbird EsrApplication
Affected:< 10.0.8
ThunderbirdApplication
Affected:< 16.0

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
M
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:M/Au:N/C:C/I:C/A:C

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. Check Firefox version on Linux
    Run: firefox --version or dpkg -l | grep firefox or rpm -qa | grep firefox
    Affected if Version is less than 10.0.8 OR between 10.0.8 and 16.0 (exclusive)
  2. Check Thunderbird version on Linux
    Run: thunderbird --version or dpkg -l | grep thunderbird or rpm -qa | grep thunderbird
    Affected if Version is less than 10.0.8 OR between 10.0.8 and 16.0 (exclusive)
  3. Check Firefox version on Windows or Mac
    Open Firefox, click Help > About Firefox, or check Program Files/Firefox folder for version file
    Affected if Version displayed is less than 10.0.8 OR between 10.0.8 and 16.0 (exclusive)
  4. Check Thunderbird version on Windows or Mac
    Open Thunderbird, click Help > About Thunderbird, or check Program Files/Thunderbird folder for version file
    Affected if Version displayed is less than 10.0.8 OR between 10.0.8 and 16.0 (exclusive)

A user is affected if Firefox, Thunderbird, or SeaMonkey is installed with a version lower than 10.0.8, or any version from 10.0.8 up to but not including 16.0, since the vulnerability exists in the IsCSSWordSpacingSpace CSS parsing function in those ranges.

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.

dbcve · scoped
Upgrade available Upgrade to 10.0.8 / 16.0 or later
Fixed in 10.0.816.0
Interim mitigation

Upgrade to Firefox 16.0+, Firefox ESR 10.0.8+, Thunderbird 16.0+, Thunderbird ESR 10.0.8+, or SeaMonkey 2.13+ to patch the vulnerability.

Recommended fix High confidence

Firefox 16.0 (or Firefox ESR 10.0.8), Thunderbird 16.0 (or Thunderbird ESR 10.0.8), or SeaMonkey 2.13

  1. 1. Identify the affected Mozilla product (Firefox, Thunderbird ESR, Thunderbird, or SeaMonkey) installed in the environment.
  2. 2. Check the currently installed version of the product (e.g., via 'firefox --version', 'thunderbird --version', or 'seamonkey --version').
  3. 3. For Firefox users: Upgrade to Firefox 16.0 or later, or to Firefox ESR 10.0.8 if requiring extended support.
  4. 4. For Thunderbird users: Upgrade to Thunderbird 16.0 or later, or to Thunderbird ESR 10.0.8 if requiring extended support.
  5. 5. For SeaMonkey users: Upgrade to SeaMonkey 2.13 or later.
  6. 6. Obtain the upgrade from the official Mozilla website (https://www.mozilla.org/) or your distribution's package manager.
  7. 7. After upgrade, verify the new version is installed correctly and test that the application launches without errors.
Caveat Major version upgrades to Firefox/Thunderbird 16.0 may introduce compatibility issues with older extensions or plugins; SeaMonkey 2.13 is a comparable major version change

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,600
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,960.

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-2012-3995 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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