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FirefoxWeb browser · Mozilla

CVE-2015-2740

HIGH · 10.0 CVSS v2.0 Published 2015-07-06
Fix available
A fix is available. Upgrade to after 38.1.0 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
Buffer overflow in the nsXMLHttpRequest::AppendToResponseText function in Mozilla Firefox before 39.0, Firefox ESR 31.x before 31.8 and 38.x before 38.1, and Thunderbird before 38.1 might allow remote attackers to cause a denial of service or have unspecified other impact via unknown vectors.

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

Buffer overflow in Mozilla Firefox and Thunderbird's nsXMLHttpRequest::AppendToResponseText function allows remote attackers to cause denial of service or potentially execute arbitrary code via malformed XMLHttpRequest responses.

MitigationUpdate affected Mozilla products to patched versions: Firefox 39.0+, Firefox ESR 31.8+, Firefox ESR 38.1+, or Thunderbird 38.1+. Apply via vendor security updates or enterprise patch management.

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:= 31.0= 31.1.0= 31.1.1= 31.3.0= 31.5.1= 31.5.2= 31.5.3= 38.0<= 38.1.0
Firefox EsrWeb browser
Affected:= 31.1= 31.2= 31.3= 31.4= 31.5= 31.6.0= 31.7.0
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 14.10= 15.04
Debian LinuxOperating system
Affected:= 7.0= 8.0
ThunderbirdApplication
Affected:<= 38.0.1
Suse Linux Enterprise Software Development KitApplication
Affected:= 12.0
Suse Linux Enterprise DesktopOperating system
Affected:= 12.0
Suse Linux Enterprise ServerOperating system
Affected:= 11= 12.0

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 if Firefox or Thunderbird is installed. On Windows, look in Program Files. On Linux, run 'dpkg -l | grep -i firefox' or 'dpkg -l | grep -i thunderbird'. On RPM systems, run 'rpm -qa | grep -i firefox' or 'rpm -qa | grep -i thunderbird'.
    Affected if Firefox or Thunderbird is installed and the version matches the affected ranges below.
  2. Determine Firefox version
    For Firefox, type 'about:support' in the address bar and look at the Version field, or run 'firefox --version' from command line.
    Affected if Version is 31.0, 31.1.0, 31.1.1, 31.3.0, 31.5.1, 31.5.2, 31.5.3, 38.0, or 38.1.0 (any version <= 38.1.0 that matches these specific releases), or for ESR: 31.1 through 31.7.0 inclusive.
  3. Determine Thunderbird version
    For Thunderbird, type 'about:support' in the address bar and look at the Version field, or run 'thunderbird --version' from command line.
    Affected if Version is 38.0.1 or any earlier version (any version <= 38.0.1).
  4. Confirm XMLHttpRequest usage context
    This vulnerability is triggered when the browser processes malformed XMLHttpRequest responses. Any web content or extension using XMLHttpRequest could trigger this. There is no configuration to disable; the vulnerable code runs whenever XHR responses are processed.
    Affected if The affected Firefox or Thunderbird version processes web content with XMLHttpRequest responses.

You are affected if Mozilla Firefox (versions 31.x through 38.1.0, or ESR 31.1 through 31.7.0) or Thunderbird (version 38.0.1 or earlier) is installed and processes web content or email that contains malicious XMLHttpRequest responses.

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 38.1.0
Interim mitigation

Update affected Mozilla products to patched versions: Firefox 39.0+, Firefox ESR 31.8+, Firefox ESR 38.1+, or Thunderbird 38.1+. Apply via vendor security updates or enterprise patch management.

Recommended fix High confidence

Firefox 39.0+; Firefox ESR 31.8+ or 38.1+; Thunderbird 38.1+

  1. Check current Firefox/Thunderbird version by navigating to Help > About in the application
  2. Back up your browser profile (located in ~/.mozilla/firefox/ on Linux or %APPDATA%\Mozilla\Firefox\Profiles on Windows)
  3. Update Firefox to version 39.0 or later via the application's built-in update mechanism (Help > About > Check for Updates) or download from https://www.mozilla.org/firefox/
  4. For Firefox ESR 31.x users, upgrade to ESR 31.8 or later; for Firefox ESR 38.x users, upgrade to ESR 38.1 or later
  5. For Thunderbird users, upgrade to version 38.1 or later via Help > About > Check for Updates or download from https://www.thunderbird.net/
  6. After upgrade, verify the installed version matches or exceeds the fixed release
Caveat Major version upgrades (e.g., 31.x to 39.x) may have compatibility impacts with older extensions or add-ons; test in a non-production environment first

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2015-2740 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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