dbcve.org
FirefoxWeb browser · Mozilla

CVE-2022-31739

HIGH · 8.8 CVSS v3.1 Published 2022-12-22
Fix available
A fix is available. Upgrade to 91.10 / 101 or later.
See remediation →
95/100
Remediation priority · Urgent
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
When downloading files on Windows, the % character was not escaped, which could have lead to a download incorrectly being saved to attacker-influenced paths that used variables such as %HOMEPATH% or %APPDATA%.<br>*This bug only affects Firefox for Windows. Other operating systems are unaffected.*. This vulnerability affects Thunderbird < 91.10, Firefox < 101, and Firefox ESR < 91.10.

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

On Windows, the Firefox download function failed to escape the % character in filenames. Since Windows uses %VARIABLE% syntax for environment variables like %HOMEPATH% or %APPDATA%, an attacker could craft a malicious filename to redirect the downloaded file to an attacker-controlled location, achieving arbitrary file write.

MitigationUpdate to Firefox 101+, Firefox ESR 91.10+, or Thunderbird 91.10+ to receive the patch that properly escapes the % character in download filenames on Windows.

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:< 101
Firefox EsrWeb browser
Affected:< 91.10
ThunderbirdApplication
Affected:< 91.10

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 which Mozilla product is installed
    Open the application and go to Help > About [Product Name], or check Add/Remove Programs for Mozilla Firefox or Mozilla Thunderbird
    Affected if Any of Firefox, Firefox ESR, or Thunderbird is installed on Windows
  2. Check Firefox version on Windows
    In Firefox, navigate to Help > About Firefox. Note the version number displayed (e.g., 100.0, 91.9)
    Affected if The version shown is below 101 (for Firefox) or below 91.10 (for Firefox ESR)
  3. Check Thunderbird version on Windows
    In Thunderbird, navigate to Help > About Thunderbird. Note the version number displayed
    Affected if The version shown is below 91.10
  4. Verify the Windows platform
    This vulnerability only affects Windows systems. Confirm the operating system is Windows by checking System Properties or running 'winver' in Run dialog
    Affected if The system is running Windows and the installed Mozilla product version falls below the fixed releases

A user is affected if they are running Firefox below version 101, Firefox ESR below 91.10, or Thunderbird below 91.10 on Windows, where a specially crafted filename containing % characters during a download could redirect the file to an unintended location.

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 91.10 / 101 or later
Fixed in 91.10101
Interim mitigation

Update to Firefox 101+, Firefox ESR 91.10+, or Thunderbird 91.10+ to receive the patch that properly escapes the % character in download filenames on Windows.

Recommended fix High confidence

Firefox 101, Firefox ESR 91.10, or Thunderbird 91.10 (or later)

  1. 1. Open Firefox or Thunderbird and navigate to Help > About to check the current installed version
  2. 2. If the version is below 101 (Firefox) or below 91.10 (Thunderbird/Firefox ESR), proceed to update
  3. 3. For Firefox: Download Firefox 101 or later from the official Mozilla website (www.mozilla.org)
  4. 4. For Thunderbird: Download Thunderbird 91.10 or later from the official Mozilla website (www.mozilla.org)
  5. 5. For Firefox ESR: Download Firefox ESR 91.10 or later from the official Mozilla website (www.mozilla.org)
  6. 6. Run the installer and complete the installation
  7. 7. Restart the application and verify the version in Help > About shows the patched release
Caveat Upgrading to new major versions may introduce minor UI changes; ensure compatibility with any required browser extensions or enterprise policies before deploying

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2022-31739 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2022-31739 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