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FirefoxWeb browser · Mozilla

CVE-2013-5596

MEDIUM · 6.8 CVSS v2.0 Published 2013-10-30
Fix available
A fix is available. Upgrade to after 24.0.1 or later.
See remediation →
77/100
Remediation priority · High
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 cycle collection (CC) implementation in Mozilla Firefox before 25.0, Firefox ESR 24.x before 24.1, Thunderbird before 24.1, and SeaMonkey before 2.22 does not properly determine the thread for release of an image object, which allows remote attackers to execute arbitrary code or cause a denial of service (race condition and application crash) via a large HTML document containing IMG elements, as demonstrated by the Never-Ending Reddit on reddit.com.

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

The cycle collection (CC) implementation in Mozilla products fails to properly determine the correct thread for releasing an image object, creating a race condition where image objects may be released from the wrong thread context. This can lead to use-after-free conditions enabling arbitrary code execution or cause denial of service via application crashes when processing large HTML documents with multiple IMG elements.

MitigationUpdate affected Mozilla products to Firefox 25.0 or later, Firefox ESR 24.1 or later, Thunderbird 24.1 or later, or SeaMonkey 2.22 or later to patch the cycle collector threading flaw.

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:= 24.0= 24.0.1= 24.0.2<= 24.0= 19.0= 19.0.1= 19.0.2= 20.0= 20.0.1= 21.0= 22.0= 23.0
ThunderbirdApplication
Affected:<= 24.0.1= 17.0= 17.0.1= 17.0.2= 17.0.3= 17.0.4= 17.0.5= 17.0.6= 17.0.7= 17.0.8= 24.0
Thunderbird EsrApplication
Affected:= 17.0.9
SeamonkeyApplication
Affected:<= 2.22= 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
Partial
Integrity
Partial
Availability
Partial

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

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 which Mozilla product is installed: Firefox, Thunderbird, Thunderbird ESR, or SeaMonkey. On Windows check Add/Remove Programs or the application executable properties. On Linux check package manager or application launchers. On Mac check Applications folder.
    Affected if Any of the four affected products (Firefox, Thunderbird, Thunderbird ESR, or Seamonkey) are installed
  2. Determine product version
    For Firefox: Go to Help > About Firefox. For Thunderbird: Go to Help > About Thunderbird. For SeaMonkey: Go to Help > About SeaMonkey. Record the exact version number displayed.
    Affected if Version matches any of the affected versions listed in the CVE (Firefox 19.x-24.x, Thunderbird 17.x-24.x, Thunderbird ESR 17.0.9, Seamonkey 2.0.x-2.22)
  3. Compare against affected version ranges
    Compare your installed version to the known affected ranges: Firefox 19.0-24.0.2 (excluding 25.0+), Thunderbird 17.0-24.0.1 (excluding 24.1+), Thunderbird ESR 17.0.9 (only), Seamonkey 2.0-2.22 (excluding newer versions).
    Affected if Installed version falls within any of the affected version ranges specified in the CVE
  4. Verify application usage context
    The vulnerability triggers when processing large HTML documents with multiple IMG elements. If the application is used to render or display HTML content with images, the race condition in cycle collection can occur.
    Affected if The application is used to view HTML pages containing multiple images, which activates the vulnerable image object cycle collection code path

If a Mozilla product (Firefox, Thunderbird, or SeaMonkey) is installed and its version falls within the affected ranges (19.x-24.x for Firefox, 17.x-24.x for Thunderbird, any version up to 2.22 for SeaMonkey), the environment is vulnerable to this cycle collector race condition.

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.

From vendor data
Upgrade available Upgrade to a release after 24.0.1
Interim mitigation

Update affected Mozilla products to Firefox 25.0 or later, Firefox ESR 24.1 or later, Thunderbird 24.1 or later, or SeaMonkey 2.22 or later to patch the cycle collector threading flaw.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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-2013-5596 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