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FirefoxWeb browser · Mozilla

CVE-2017-7765

HIGH · 7.5 CVSS v3.0 Published 2018-06-11
Fix available
A fix is available. Upgrade to 52.2.0 / 54.0 or later.
See remediation →
84/100
Remediation priority · High
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
The "Mark of the Web" was not correctly saved on Windows when files with very long names were downloaded from the Internet. Without the Mark of the Web data, the security warning that Windows displays before running executables downloaded from the Internet is not shown. Note: This attack only affects Windows operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

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

When Firefox or Thunderbird on Windows downloads files with very long names, the 'Mark of the Web' (MOTW) metadata is not correctly attached to the file. MOTW is a Windows security feature that identifies files as originating from the Internet and triggers a security warning before execution. Without this marker, downloaded executables run without the expected user warning, allowing potentially malicious code to execute unchecked.

MitigationUpdate to Firefox 54 or later, Firefox ESR 52.2 or later, or Thunderbird 52.2 or later. This is a client-side application vulnerability fixed via software update.

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:< 52.2.0< 54.0
ThunderbirdApplication
Affected:< 52.2.0

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
None
Integrity
High
Availability
None

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

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 the operating system
    Check if the system is running Windows (MOTW is a Windows-specific security feature; this vulnerability does not affect other OSes)
    Affected if The system is running Windows and the installed Firefox/Thunderbird version falls within the affected ranges
  2. Check Firefox version
    In Firefox, navigate to Help > About Firefox, or enter 'about:support' in the address bar, to view the version number
    Affected if Firefox version is below 54.0, or between 52.2.0 and 53.x
  3. Check Thunderbird version
    In Thunderbird, navigate to Help > About Thunderbird to view the version number
    Affected if Thunderbird version is below 52.2.0
  4. Identify recently downloaded files with long names
    On Windows, open the Downloads folder and sort by name to identify files with unusually long filenames that were downloaded using the affected browser or mail client
    Affected if Files with very long names (typically exceeding 100+ characters) were downloaded using the vulnerable application
  5. Verify Mark of the Web status on downloaded executables
    Open PowerShell and run 'Get-Content -Path "<file_path>" -TotalCount 1 -Encoding Byte' to check for the 'Zone.Identifier' alternate data stream, or right-click the file > Properties > General tab to see if there is a 'Security' warning indicating it was downloaded from the Internet
    Affected if An executable file downloaded with a long name shows no Internet zone marker in its properties or lacks the Zone.Identifier stream

A user is affected if running Windows with Firefox below 54.0 (or between 52.2.0-53.x) or Thunderbird below 52.2.0, and has downloaded executable files with unusually long filenames that lack the Mark of the Web zone identifier.

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.

From vendor data
Upgrade available Upgrade to 52.2.0 / 54.0 or later
Fixed in 52.2.054.0
Interim mitigation

Update to Firefox 54 or later, Firefox ESR 52.2 or later, or Thunderbird 52.2 or later. This is a client-side application vulnerability fixed via software update.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 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.

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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-2017-7765 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