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FirefoxWeb browser · Mozilla

CVE-2023-29539

HIGH · 8.8 CVSS v3.1 Published 2023-06-02
Fix available
A fix is available. Upgrade to 102.10 / 112.0 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 handling the filename directive in the Content-Disposition header, the filename would be truncated if the filename contained a NULL character. This could have led to reflected file download attacks potentially tricking users to install malware. This vulnerability affects Firefox < 112, Focus for Android < 112, Firefox ESR < 102.10, Firefox for Android < 112, and Thunderbird < 102.10.

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

Mozilla browsers fail to properly handle NULL characters in the filename directive of Content-Disposition headers. When a filename contains a NULL character, the browser truncates the filename at that point while preserving the actual file extension, causing 'malware.txt\x00.exe' to display as 'malware.txt' to users, facilitating reflected file download attacks.

MitigationUpdate affected Mozilla products to Firefox 112, Firefox ESR 102.10, Thunderbird 102.10, or later versions to patch the NULL character truncation vulnerability.

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:< 112.0
Firefox EsrWeb browser
Affected:< 102.10
FocusApplication
Affected:< 112.0
ThunderbirdApplication
Affected:< 102.10

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 installed Mozilla product
    Determine which Mozilla browser or application is in use: Firefox (regular), Firefox ESR, Thunderbird, or Focus. Check installed programs or about:support page.
    Affected if Any of these products are installed
  2. Determine Firefox version
    For Firefox: Open menu > Help > About Firefox, or navigate to about:support. Note the version number displayed.
    Affected if Firefox version is below 112.0
  3. Determine Firefox ESR version
    For Firefox ESR: Open menu > Help > About Firefox, or navigate to about:support. Note the version number displayed (includes ESR designation).
    Affected if Firefox ESR version is below 102.10
  4. Determine Thunderbird version
    For Thunderbird: Open menu > Help > About Thunderbird. Note the version number displayed.
    Affected if Thunderbird version is below 102.10
  5. Determine Mozilla Focus version
    For Focus: Check the app version in the device's app settings or about:support page within the browser.
    Affected if Mozilla Focus version is below 112.0

If any installed Mozilla product (Firefox, Firefox ESR, Thunderbird, or Focus) matches a version below 112.0 (Firefox/Focus) or below 102.10 (Firefox ESR/Thunderbird), the environment is vulnerable to CVE-2023-29539.

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 102.10 / 112.0 or later
Fixed in 102.10112.0
Interim mitigation

Update affected Mozilla products to Firefox 112, Firefox ESR 102.10, Thunderbird 102.10, or later versions to patch the NULL character truncation vulnerability.

Recommended fix High confidence

Firefox 112.0, Firefox ESR 102.10, Thunderbird 102.10, Focus for Android 112.0

  1. Check current Firefox version by navigating to menu > Help > About Firefox (or enter 'about:support' in address bar)
  2. Check current Thunderbird version by navigating to menu > Help > About Thunderbird
  3. For Firefox ESR, verify the installed ESR version through about:support
  4. Download the latest Firefox 112.0 or later from www.mozilla.org/firefox/
  5. Download Thunderbird 102.10 or later from www.mozilla.org/thunderbird/
  6. Download Firefox ESR 102.10 or later from www.mozilla.org/firefox/all/
  7. For Android Focus, update through Google Play Store to version 112.0 or later
  8. Restart the application after updating
Caveat Users on older systems may need to check system requirements for Firefox 112; some older extensions or configurations may not be compatible with major version updates

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
3.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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-2023-29539 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