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Debian LinuxOperating system · Debian

CVE-2018-5104

CRITICAL · 9.8 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to 52.6.0 / 58.0 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
A use-after-free vulnerability can occur during font face manipulation when a font face is freed while still in use, resulting in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.6, Firefox ESR < 52.6, and Firefox < 58.

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 use-after-free vulnerability in the font rendering subsystem allows a font face to be deallocated while still actively referenced in memory. This leads to a dangling pointer that can be exploited for remote code execution when the application attempts to access the freed font data.

MitigationApply vendor-supplied patches by updating Thunderbird to >=52.6, Firefox ESR to >=52.6, or Firefox to >=58.

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
Debian LinuxOperating system
Affected:= 7.0= 8.0= 9.0
Enterprise Linux DesktopOperating system
Affected:= 6.0= 7.0
Enterprise Linux ServerOperating system
Affected:= 6.0= 7.0
Enterprise Linux Server AusOperating system
Affected:= 7.4
Enterprise Linux Server EusOperating system
Affected:= 7.4= 7.5
Enterprise Linux WorkstationOperating system
Affected:= 6.0= 7.0
FirefoxWeb browser
Affected:< 58.0< 52.6.0
Ubuntu LinuxOperating system
Affected:= 14.04= 16.04= 17.10

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

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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. Check if Mozilla Firefox is installed
    Run 'which firefox' or check package manager: 'dpkg -l | grep firefox' on Debian/Ubuntu, 'rpm -qa | grep firefox' on RHEL
    Affected if Firefox is not installed - the system is not affected by this Firefox vulnerability
  2. Determine Firefox version number
    Execute 'firefox --version' or look in Firefox menu > Help > About. For package-based systems, also try 'dpkg -l firefox' or 'rpm -q firefox'
    Affected if Version is less than 52.6.0 for ESR releases, or less than 58.0 for standard releases - the version falls within the affected range (< 52.6.0 or < 58.0)
  3. Identify the Linux distribution and version
    Check /etc/os-release, /etc/redhat-release, /etc/debian_version, or run 'lsb_release -a'
    Affected if Running Debian 7.0, 8.0, or 9.0; Ubuntu 14.04, 16.04, or 17.10; or RHEL 6.x/7.x without Firefox patches applied - the OS version matches affected Debian/Ubuntu/RHEL releases
  4. Verify font rendering feature is in use
    This vulnerability affects the font rendering subsystem. Confirm Firefox has been used to render web pages with custom fonts, or that gfx.font_rendering.* preferences have not been disabled
    Affected if Firefox is actively used with default font rendering settings - the use-after-free condition can trigger during font operations

A user is affected if they run Firefox versions below 52.6.0 (ESR) or below 58.0 (standard) on any of the listed affected Linux distributions (Debian 7/8/9, Ubuntu 14.04/16.04/17.10, or RHEL 6.x/7.x), with font rendering enabled and active browser usage.

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 52.6.0 / 58.0 or later
Fixed in 52.6.058.0
Interim mitigation

Apply vendor-supplied patches by updating Thunderbird to >=52.6, Firefox ESR to >=52.6, or Firefox to >=58.

Recommended fix High confidence

Firefox 58.0+, Firefox ESR 52.6.0+, or Thunderbird 52.6+

  1. Identify the installed Mozilla product (Firefox, Firefox ESR, or Thunderbird) by checking the application version
  2. For Debian/Ubuntu systems: Run 'apt-get update && apt-get install firefox firefox-esr thunderbird' to upgrade to the latest available version in the repository
  3. For RHEL/CentOS systems: Run 'yum update firefox firefox-esr thunderbird' or 'dnf update firefox firefox-esr thunderbird'
  4. Alternatively, download the specific fixed version directly from Mozilla: Firefox 58.0 or later, Firefox ESR 52.6.0 or later, or Thunderbird 52.6 or later from https://www.mozilla.org/
  5. After upgrade, restart the application and verify the version with 'firefox --version', 'firefox-esr --version', or 'thunderbird --version'
  6. Ensure the upgraded version is 58.0 or higher for Firefox, 52.6.0 or higher for Firefox ESR, or 52.6 or higher for Thunderbird
Caveat Firefox 58+ may have minor web compatibility changes; some legacy extensions may be incompatible; profile migration from older versions is generally seamless

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

Fix this in Debian Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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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-2018-5104 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