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FirefoxWeb browser · Mozilla

CVE-2023-5176

CRITICAL · 9.8 CVSS v3.1 Published 2023-09-27
Fix available
A fix is available. Upgrade to 115.3 / 118 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
Memory safety bugs present in Firefox 117, Firefox ESR 115.2, and Thunderbird 115.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 118, Firefox ESR < 115.3, and Thunderbird < 115.3.

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

Multiple memory safety bugs in Firefox and Thunderbird allowed memory corruption that could potentially be exploited for arbitrary code execution. The vulnerabilities stem from unspecified memory handling issues in the browser engine.

MitigationUpdate affected installations to Firefox 118+, Firefox ESR 115.3+, or Thunderbird 115.3+ to patch the memory safety vulnerabilities.

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:< 118
Firefox EsrWeb browser
Affected:< 115.3
Debian LinuxOperating system
Affected:= 10.0= 11.0= 12.0
ThunderbirdApplication
Affected:< 115.3

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:3.1/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. Identify installed Mozilla product
    Check if Firefox or Thunderbird is installed. On Linux: which firefox thunderbird; On Windows: check Program Files for Mozilla Firefox or Mozilla Thunderbird folders; On macOS: check /Applications for Firefox or Thunderbird.
    Affected if Neither Firefox nor Thunderbird is installed (not affected)
  2. Determine Firefox version
    Firefox: Help > About Firefox, or run firefox --version in terminal. Firefox ESR: Check firefox-esr --version. Windows: Look in the application folder for version info or right-click executable > Properties > Details.
    Affected if Version is less than 118 for Firefox, or less than 115.3 for Firefox ESR
  3. Determine Thunderbird version
    Thunderbird: Help > About Thunderbird, or run thunderbird --version in terminal. Windows: Look in the application folder for version info or right-click executable > Properties > Details.
    Affected if Version is less than 115.3
  4. Check Debian package versions
    On Debian-based systems, run: dpkg -l | grep -i firefox or dpkg -l | grep -i thunderbird to list installed Mozilla package versions from Debian repositories.
    Affected if Running Debian 10, 11, or 12 with unpatched Mozilla packages from distribution repositories

You are affected if you have Firefox versions below 118 (or ESR below 115.3) or Thunderbird versions below 115.3 installed from any source, including Debian repositories on versions 10-12.

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 115.3 / 118 or later
Fixed in 115.3118
Interim mitigation

Update affected installations to Firefox 118+, Firefox ESR 115.3+, or Thunderbird 115.3+ to patch the memory safety vulnerabilities.

Recommended fix High confidence

Firefox 118, Firefox ESR 115.3, Thunderbird 115.3

  1. Upgrade Firefox to version 118 or later
  2. Upgrade Firefox ESR to version 115.3 or later
  3. Upgrade Thunderbird to version 115.3 or later

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
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

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-2023-5176 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