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FirefoxWeb browser · Mozilla

CVE-2009-0771

HIGH · 10.0 CVSS v2.0 Published 2009-03-05
Fix available
A fix is available. Upgrade to after 3.0.6 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 layout engine in Mozilla Firefox before 3.0.7, Thunderbird before 2.0.0.21, and SeaMonkey 1.1.15 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via certain vectors that trigger memory corruption and assertion failures.

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 · moderate confidence

Memory corruption vulnerability in the layout engine of Firefox before 3.0.7, Thunderbird before 2.0.0.21, and SeaMonkey 1.1.15 allows remote attackers to crash the application or potentially execute arbitrary code via crafted vectors that trigger assertion failures.

MitigationUpdate affected Mozilla products to patched versions (Firefox 3.0.7+, Thunderbird 2.0.0.21+, SeaMonkey 1.1.15+) or migrate to currently supported versions, as these legacy versions are end-of-life and no longer receive security updates.

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= 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:<= 1.1.14= 1.0= 1.0.1= 1.0.2= 1.0.3= 1.0.5= 1.0.6= 1.0.7= 1.0.8= 1.0.9= 1.1= 1.1.1
ThunderbirdApplication
Affected:<= 2.0.0.20= 2.0.0.0= 2.0.0.4= 2.0.0.5= 2.0.0.6= 2.0.0.9= 2.0.0.12= 2.0.0.14= 2.0.0.16= 2.0.0.17= 2.0.0.18= 2.0.0.19

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
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:L/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 installed Mozilla product
    Check for Firefox, Thunderbird, or SeaMonkey executables in standard installation directories (e.g., C:\Program Files\Mozilla Firefox, C:\Program Files\Mozilla Thunderbird, C:\Program Files\SeaMonkey) or list installed programs via system settings
    Affected if Any of these three products are installed
  2. Check Firefox version
    Run 'firefox --version' from command line or open Firefox and navigate to Help > About Firefox
    Affected if Version is 3.0.6 or earlier, or any 1.0.x or 1.5.x release listed in the affected versions
  3. Check Thunderbird version
    Run 'thunderbird --version' from command line or open Thunderbird and navigate to Help > About Thunderbird
    Affected if Version is 2.0.0.20 or earlier, or any specific 2.0.0.x release listed in the affected versions
  4. Check SeaMonkey version
    Run 'seamonkey --version' from command line or open SeaMonkey and navigate to Help > About SeaMonkey
    Affected if Version is 1.1.14 or earlier, or any 1.0.x or 1.1.x release listed in the affected versions

If any of these Mozilla products are installed and the version matches or falls within the affected ranges specified (Firefox <= 3.0.6, Thunderbird <= 2.0.0.20, SeaMonkey <= 1.1.14), the environment is vulnerable to CVE-2009-0771.

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 3.0.6
Interim mitigation

Update affected Mozilla products to patched versions (Firefox 3.0.7+, Thunderbird 2.0.0.21+, SeaMonkey 1.1.15+) or migrate to currently supported versions, as these legacy versions are end-of-life and no longer receive security updates.

Recommended fix High confidence

Firefox 3.0.7+; Thunderbird 2.0.0.21+; SeaMonkey 1.1.15+ (or migrate to supported modern versions)

  1. For Firefox users: Upgrade to Firefox 3.0.7 or later. If using Firefox 1.0.x, migrate to a supported version as 1.0.x is no longer maintained.
  2. For Thunderbird users: Upgrade to Thunderbird 2.0.0.21 or later.
  3. For Seamonkey users: Upgrade to Seamonkey 1.1.15 or later. If using Seamonkey 1.0.x, migrate to a supported version as 1.0.x is no longer maintained.
  4. After upgrading, verify the version by checking Help > About in the application menu to confirm the installed version matches or exceeds the fixed release.
Caveat Very old extensions and plugins may be incompatible with newer versions; legacy systems relying on Firefox 1.0.x or Seamonkey 1.0.x may require application rewrites for modern browser adoption

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

Scan for this in your stack

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dbcve dependency scanner

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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-2009-0771 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