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Debian LinuxOperating system · Debian

CVE-2018-5091

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 WebRTC connections when interacting with the DTMF timers. This results in a potentially exploitable crash. This vulnerability affects 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 exists in Firefox's WebRTC implementation when handling DTMF (Dual-Tone Multi-Frequency) timers. The vulnerability allows memory to be accessed after being freed, potentially leading to arbitrary code execution or a crash.

MitigationUpdate Firefox to version 58 or later, or Firefox ESR to version 52.6 or later, to patch the use-after-free in the WebRTC DTMF timer handling.

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 LinuxOperating system
Affected:= 6.0= 7.0
Enterprise Linux DesktopOperating system
Affected:= 6.0= 7.0
Enterprise Linux ServerOperating system
Affected:= 6.0= 7.0
Enterprise Linux Server AusOperating system
Affected:= 7.3= 7.4
Enterprise Linux Server EusOperating system
Affected:= 7.3= 7.4= 7.5
Enterprise Linux WorkstationOperating system
Affected:= 6.0= 7.0
FirefoxWeb browser
Affected:< 58.0< 52.6.0

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
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 Firefox is installed
    Run 'which firefox' or 'rpm -q firefox' on RHEL systems, or 'dpkg -l firefox' on Debian systems
    Affected if Firefox is not installed - not affected
  2. Determine installed Firefox version
    Run 'firefox --version' or check the package version via 'rpm -q firefox' / 'dpkg -l firefox'
    Affected if Version is less than 58.0, or version is between 52.0 and 52.5.x (ESR versions below 52.6)
  3. Check for Firefox ESR version
    Run 'firefox --version' and look for 'ESR' in the output, or check package details
    Affected if ESR version is less than 52.6.0 (for example, 52.5.x or earlier)
  4. Verify WebRTC support is present
    Check if WebRTC is available in the Firefox installation by typing 'about:support' in the address bar and looking for WebRTC components, or check for webrtc* packages
    Affected if WebRTC support is present in the Firefox installation
  5. Check OS version for packaged Firefox
    Run 'cat /etc/os-release' on Debian or 'cat /etc/redhat-release' on RHEL to identify the OS version
    Affected if Running Debian 7.0, 8.0, or 9.0; or RHEL 6.x or 7.x variants with an unpatched Firefox version

You are affected if Firefox (or Firefox ESR) version is below 58.0 (or below 52.6.0 for ESR) and WebRTC functionality is present in the installation on a vulnerable OS version.

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

Update Firefox to version 58 or later, or Firefox ESR to version 52.6 or later, to patch the use-after-free in the WebRTC DTMF timer handling.

Recommended fix High confidence

Firefox 58.0 or later (standard), Firefox ESR 52.6.0 or later

  1. Identify the installed Firefox version by navigating to Menu > Help > About Firefox (or typing 'about:support' in the address bar)
  2. For Debian systems: Run 'apt-get update && apt-get upgrade' to receive the fixed Firefox package from Debian security repositories
  3. For RHEL/CentOS systems: Run 'yum update firefox' to receive the fixed Firefox package from Red Hat repositories
  4. Alternatively, download Firefox 58.0 or later directly from the official Mozilla website (getfirefox.com)
  5. Alternatively, download Firefox ESR 52.6 or later from Mozilla for enterprise deployments
  6. Restart Firefox after upgrading to ensure the new version is loaded
  7. Verify the fix by checking the Firefox version (should be >= 58.0 or >= 52.6.0 for ESR)
Caveat Minimal risk - standard browser upgrade. Some legacy WebRTC features may have been deprecated, and minor UI changes between versions are possible.

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

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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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-2018-5091 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