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FirefoxWeb browser · Mozilla

CVE-2024-3859

MEDIUM · 5.9 CVSS v3.1 Published 2024-04-16
Fix available
A fix is available. Upgrade to 115.10 / 125.0 or later.
See remediation →
66/100
Remediation priority · Elevated
Remotely reachable No privileges

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
On 32-bit versions there were integer-overflows that led to an out-of-bounds-read that potentially could be triggered by a malformed OpenType font. This vulnerability affects Firefox < 125, Firefox ESR < 115.10, and Thunderbird < 115.10.

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

Integer overflow vulnerabilities in 32-bit versions of Firefox, Firefox ESR, and Thunderbird during OpenType font parsing lead to out-of-bounds memory reads. A malformed OpenType font file can trigger these overflows, potentially allowing an attacker to read sensitive memory contents.

MitigationUpdate all 32-bit installations of Firefox to version 125 or higher, Firefox ESR to 115.10 or higher, and Thunderbird to 115.10 or higher to receive the security patch.

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:< 115.10< 125.0
Debian LinuxOperating system
Affected:= 10.0
ThunderbirdApplication
Affected:< 115.10

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
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:N

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
    Check if Firefox or Thunderbird is installed by looking for the executable in common locations: C:\Program Files\Mozilla Firefox\firefox.exe (64-bit) or C:\Program Files (x86)\Mozilla Firefox\firefox.exe (32-bit) on Windows; /usr/bin/firefox or /usr/bin/thunderbird on Linux
    Affected if The product is Firefox or Thunderbird
  2. Determine if the installation is 32-bit
    On Windows, check the Program Files (x86) folder or right-click the executable > Properties > Details to see the Bitness. On Linux, run: file /usr/bin/firefox or dpkg --print-architecture for the package architecture
    Affected if The application is running as a 32-bit (x86) build - this CVE only affects 32-bit versions
  3. Check the installed Firefox version
    For Firefox: Run firefox --version from command line, or go to Help > About Firefox. For Thunderbird: Run thunderbird --version, or go by Help > About Thunderbird
    Affected if The version is below 115.10 or below 125.0 (depending on the release channel)
  4. Verify OpenType font processing is available
    Open any webpage or email with an embedded font, or check that the application can display documents with custom fonts. The vulnerability triggers when parsing malformed OpenType fonts
    Affected if The application can process OpenType fonts (this is enabled by default)

You are affected if you are running a 32-bit version of Firefox below 115.10 (or below 125.0 for certain release channels) or Thunderbird below 115.10, and the application can process OpenType font files.

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 115.10 / 125.0 or later
Fixed in 115.10125.0
Interim mitigation

Update all 32-bit installations of Firefox to version 125 or higher, Firefox ESR to 115.10 or higher, and Thunderbird to 115.10 or higher to receive the security patch.

Recommended fix High confidence

Firefox 125.0 (or Firefox ESR 115.10), Thunderbird 115.10

  1. For Firefox: Upgrade to Firefox 125.0 or later (or Firefox ESR 115.10 or later if using ESR)
  2. For Thunderbird: Upgrade to Thunderbird 115.10 or later
  3. For Debian 10 (Buster): Apply Debian security updates for firefox-esr/thunderbird packages, or upgrade to a newer Debian release that receives active security support
Caveat Major version upgrades may introduce compatibility issues with older extensions or plugins; test in 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
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

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-2024-3859 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