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FirefoxWeb browser · Mozilla

CVE-2012-3962

HIGH · 9.3 CVSS v2.0 Published 2012-08-29
Fix available
A fix is available. Upgrade to after 14.0 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
Mozilla Firefox before 15.0, Firefox ESR 10.x before 10.0.7, Thunderbird before 15.0, Thunderbird ESR 10.x before 10.0.7, and SeaMonkey before 2.12 do not properly iterate through the characters in a text run, which allows remote attackers to execute arbitrary code via a crafted document.

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 products fail to properly iterate through characters in a text run during document rendering, causing memory corruption that can be exploited by remote attackers via crafted documents to achieve arbitrary code execution.

MitigationApply vendor-supplied updates: upgrade Firefox to 15.0+, Firefox ESR to 10.0.7+, Thunderbird to 15.0+, Thunderbird ESR to 10.0.7+, or SeaMonkey to 2.12+; alternatively, disable JavaScript and restrict document loading from untrusted sources until patching is feasible.

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= 10.0.1= 10.0.2= 10.0.3= 10.0.4= 10.0.5= 10.0.6<= 14.0= 1.0= 1.0.1= 1.0.2= 1.0.3
Thunderbird EsrApplication
Affected:= 10.0= 10.0.1= 10.0.2= 10.0.3= 10.0.4= 10.0.5= 10.0.6
ThunderbirdApplication
Affected:<= 14.0= 1.0= 1.0.1= 1.0.2= 1.0.3= 1.0.4= 1.0.5= 1.0.6= 1.0.7= 1.0.8= 1.5= 1.5.0.1
SeamonkeyApplication
Affected:<= 2.11= 2.0= 2.0.1= 2.0.2= 2.0.3= 2.0.4= 2.0.5= 2.0.6= 2.0.7= 2.0.8= 2.0.9= 2.0.10

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. Identify the installed Mozilla product
    Check for Firefox, Thunderbird, or SeaMonkey installation. On Windows, look in Program Files; on macOS, check /Applications; on Linux, check /usr/lib or use package manager commands like dpkg -l or rpm -qa.
    Affected if Any of Firefox, Thunderbird, or SeaMonkey is installed
  2. Determine Firefox version
    Open Firefox, click the menu button (three lines), select Help, then About Firefox. Alternatively, run 'firefox --version' from command line.
    Affected if Version is 10.0 through 10.0.6 inclusive, 14.0 or lower, or any of 1.0, 1.0.1, 1.0.2, 1.0.3
  3. Determine Thunderbird version
    Open Thunderbird, click the menu button, select Help, then About Thunderbird. Alternatively, run 'thunderbird --version' from command line.
    Affected if Version is 10.0 through 10.0.6 inclusive (ESR), 14.0 or lower, or any of 1.0 through 1.0.8, 1.5, or 1.5.0.1
  4. Determine SeaMonkey version
    Open SeaMonkey, click the menu, select Help, then About SeaMonkey. Alternatively, run 'seamonkey --version' from command line.
    Affected if Version is 2.11 or lower, or any of 2.0 through 2.0.10

The environment is affected if any installed Mozilla product matches one of the specific version numbers or version ranges listed for that product in the CVE.

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 a release after 14.0
Interim mitigation

Apply vendor-supplied updates: upgrade Firefox to 15.0+, Firefox ESR to 10.0.7+, Thunderbird to 15.0+, Thunderbird ESR to 10.0.7+, or SeaMonkey to 2.12+; alternatively, disable JavaScript and restrict document loading from untrusted sources until patching is feasible.

Recommended fix High confidence

Firefox 15.0+ (or Firefox ESR 10.0.7+), Thunderbird 15.0+ (or Thunderbird ESR 10.0.7+), SeaMonkey 2.12+

  1. Check current installed version of Firefox, Thunderbird, or SeaMonkey
  2. Backup any important data or profiles
  3. Download the fixed version from official Mozilla repositories
  4. For Firefox: upgrade to version 15.0 or later (or Firefox ESR 10.0.7+)
  5. For Thunderbird: upgrade to version 15.0 or later (or Thunderbird ESR 10.0.7+)
  6. For SeaMonkey: upgrade to version 2.12 or later
  7. Restart the application after upgrade
  8. Verify the installed version matches the fixed release
Caveat Minor: Upgrading to major version releases may have minor UI/feature changes; ensure compatibility with any required browser plugins or extensions

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA3.0 h
10.0 hours of engineering $1,750
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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-2012-3962 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