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FirefoxWeb browser · Mozilla

CVE-2009-0775

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
Double free vulnerability in Mozilla Firefox before 3.0.7, Thunderbird before 2.0.0.21, and SeaMonkey before 1.1.15 allows remote attackers to execute arbitrary code via "cloned XUL DOM elements which were linked as a parent and child," which are not properly handled during garbage collection.

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

A double free vulnerability exists in Mozilla Firefox before 3.0.7, Thunderbird before 2.0.0.21, and SeaMonkey before 1.1.15. When XUL DOM elements are cloned and linked as parent-child relationships, the garbage collector improperly handles memory deallocation, causing the same memory to be freed twice. This allows remote attackers to execute arbitrary code via crafted web pages.

MitigationUpgrade affected Mozilla products to the patched versions (Firefox 3.0.7+, Thunderbird 2.0.0.21+, SeaMonkey 1.1.15+) or later. For enterprises, deploy patches through standard patch management processes and verify complete coverage across all desktop endpoints.

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 Firefox version
    Open Firefox, go to Help > About Mozilla Firefox, or run 'firefox -v' from command line
    Affected if Version is 3.0.6 or earlier, or any 1.0.x or 1.5.x version listed in the affected ranges
  2. Identify installed Thunderbird version
    Open Thunderbird, go to Help > About Mozilla Thunderbird, or run 'thunderbird -v' from command line
    Affected if Version is 2.0.0.20 or earlier, or any 2.0.0.x version listed in the affected ranges
  3. Identify installed SeaMonkey version
    Open SeaMonkey, go to Help > About SeaMonkey, or run 'seamonkey -v' from command line
    Affected if Version is 1.1.14 or earlier, or any 1.0.x or 1.1.x version listed in the affected ranges
  4. Determine if XUL is enabled
    In Firefox, type 'about:config' in address bar and search for 'dom.allow_XUL' or similar XUL-related preferences; in Thunderbird/SeaMonkey check if extensions or add-ons using XUL are installed
    Affected if XUL functionality is enabled and the application handles cloned XUL DOM elements with parent-child relationships

A user is affected if any of these Mozilla products (Firefox <=3.0.6, Thunderbird <=2.0.0.20, SeaMonkey <=1.1.14) are installed with XUL processing enabled.

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

Upgrade affected Mozilla products to the patched versions (Firefox 3.0.7+, Thunderbird 2.0.0.21+, SeaMonkey 1.1.15+) or later. For enterprises, deploy patches through standard patch management processes and verify complete coverage across all desktop endpoints.

Recommended fix High confidence

Firefox 3.0.7+ / Thunderbird 2.0.0.21+ / SeaMonkey 1.1.15+

  1. 1. Identify the installed product (Firefox, Thunderbird, or SeaMonkey) and current version using 'Help > About' or the --version command line flag
  2. 2. For Firefox: Download and install Firefox 3.0.7 or later from the official Mozilla repository
  3. 3. For Thunderbird: Download and install Thunderbird 2.0.0.21 or later from the official Mozilla repository
  4. 4. For SeaMonkey: Download and install SeaMonkey 1.1.15 or later from the official Mozilla repository
  5. 5. After installation, restart the application and verify the new version is running via 'Help > About'
  6. 6. Test that affected functionality (XUL DOM cloning operations) works correctly
Caveat These are legacy versions from 2009; upgrading may require migration of profiles and add-ons to modern versions, which could have compatibility implications

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

Fix this in Firefox Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2009-0775 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