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FirefoxWeb browser · Mozilla

CVE-2013-0756

HIGH · 9.3 CVSS v2.0 Published 2013-01-13
Fix available
A fix is available. Upgrade to 2.15 / 17.0.2 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
Use-after-free vulnerability in the obj_toSource function in Mozilla Firefox before 18.0, Firefox ESR 17.x before 17.0.2, Thunderbird before 17.0.2, Thunderbird ESR 17.x before 17.0.2, and SeaMonkey before 2.15 allows remote attackers to execute arbitrary code via a crafted web page referencing JavaScript Proxy objects that 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

Use-after-free vulnerability in the obj_toSource function in Mozilla products. When JavaScript Proxy objects are not properly handled during garbage collection, the memory can be freed while still being referenced, leading to arbitrary code execution.

MitigationUpgrade to Firefox 18.0+, Firefox ESR 17.0.2+, Thunderbird 17.0.2+, Thunderbird ESR 17.0.2+, or SeaMonkey 2.15+ to patch the vulnerable obj_toSource function.

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:< 17.0.2< 18.0
Ubuntu LinuxOperating system
Affected:= 10.04= 11.10= 12.04= 12.10
SeamonkeyApplication
Affected:< 2.15
ThunderbirdApplication
Affected:< 17.0.2
Thunderbird EsrApplication
Affected:< 17.0.2
OpensuseOperating system
Affected:= 11.4= 12.1= 12.2
Linux Enterprise DesktopOperating system
Affected:= 10= 11
Linux Enterprise ServerOperating system
Affected:= 10= 11

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
    Determine which Mozilla application is installed (Firefox, Thunderbird, SeaMonkey) by checking the application name or examining /usr/bin/ for the executable
    Affected if Any of the affected Mozilla products are installed (Firefox, Thunderbird, SeaMonkey)
  2. Check the installed version of Firefox
    Run 'firefox --version' or check 'about:Firefox' in the address bar to determine the exact version number
    Affected if Firefox version is below 17.0.2 or between 17.0.2 and 18.0 (exclusive)
  3. Check the installed version of Thunderbird
    Run 'thunderbird --version' or check 'about:Thunderbird' in the application to determine the version
    Affected if Thunderbird version is below 17.0.2 (including all ESR versions below 17.0.2)
  4. Check the installed version of SeaMonkey
    Run 'seamonkey --version' or check 'about:SeaMonkey' in the application to determine the version
    Affected if SeaMonkey version is below 2.15
  5. Verify JavaScript Proxy object usage
    Determine if the application processes untrusted JavaScript that could contain Proxy objects, as the vulnerability is triggered when obj_toSource processes such objects during garbage collection
    Affected if The browser or application processes JavaScript code that utilizes the Proxy object API

A user is affected if they run Firefox < 18.0 (or < 17.0.2 for ESR), Thunderbird < 17.0.2, or SeaMonkey < 2.15, and process JavaScript containing Proxy objects that invoke the obj_toSource function.

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 2.15 / 17.0.2 / 18.0 or later
Fixed in 2.1517.0.218.0
Interim mitigation

Upgrade to Firefox 18.0+, Firefox ESR 17.0.2+, Thunderbird 17.0.2+, Thunderbird ESR 17.0.2+, or SeaMonkey 2.15+ to patch the vulnerable obj_toSource function.

Recommended fix High confidence

Firefox 18.0 (or Firefox ESR 17.0.2), Thunderbird 17.0.2, Thunderbird ESR 17.0.2, or SeaMonkey 2.15 - depending on which product is in use

  1. Identify the affected Mozilla product (Firefox, Firefox ESR, Thunderbird, Thunderbird ESR, or SeaMonkey) currently installed
  2. For Firefox: Upgrade to version 18.0 or later (or 17.0.2 for the ESR 17.x branch)
  3. For Thunderbird: Upgrade to version 17.0.2 or later
  4. For Thunderbird ESR: Upgrade to version 17.0.2 or later
  5. For SeaMonkey: Upgrade to version 2.15 or later
  6. Verify the upgrade was successful by checking the application's version number
  7. Restart the application completely to ensure all components are loaded from the updated version
Caveat Users on older systems may experience compatibility issues with web content designed for older JavaScript engine versions; some legacy add-ons may not be compatible with the upgraded version

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
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

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-2013-0756 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