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FortiosOperating system · Fortinet

CVE-2017-7739

MEDIUM · 6.1 CVSS v3.0 Published 2017-11-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
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
A reflected Cross-site Scripting (XSS) vulnerability in web proxy disclaimer response web pages in Fortinet FortiOS 5.6.0, 5.4.0 to 5.4.5, 5.2.0 to 5.2.11 allows an unauthenticated attacker to inject arbitrary web script or HTML in the context of the victim's browser via sending a maliciously crafted URL to the victim.

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

Reflected XSS vulnerability in FortiOS web proxy disclaimer response pages allows unauthenticated attackers to inject arbitrary JavaScript/HTML via maliciously crafted URLs. The vulnerability affects FortiOS 5.6.0, 5.4.0-5.4.5, and 5.2.0-5.2.11.

MitigationApply the appropriate FortiOS firmware update from Fortinet that addresses CVE-2017-7739. Upgrade to a patched version as specified in Fortinet's security advisory.

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
FortiosOperating system
Affected:= 5.2.0= 5.2.1= 5.2.2= 5.2.3= 5.2.4= 5.2.5= 5.2.6= 5.2.7= 5.2.8= 5.2.9= 5.2.10= 5.2.11

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
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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. Check FortiOS version
    Run 'get system status' on the FortiGate CLI or check the web UI dashboard for the firmware version
    Affected if Version is 5.2.0 through 5.2.11, 5.4.0 through 5.4.5, or 5.6.0
  2. Verify web proxy feature is enabled
    Run 'show web-proxy' or 'config web-proxy' then 'get' to display web proxy configuration settings
    Affected if Web proxy is enabled and configured with disclaimer responses
  3. Confirm disclaimer page configuration exists
    Run 'config web-proxy global' and check for 'proxy-internal' or disclaimer-related settings; look for 'explicit-web-proxy' under system interface
    Affected if Explicit web proxy with disclaimer pages is configured

You are affected if your FortiOS version falls within 5.2.0-5.2.11, 5.4.0-5.4.5, or 5.6.0 AND the explicit web proxy with disclaimer responses is enabled.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the appropriate FortiOS firmware update from Fortinet that addresses CVE-2017-7739. Upgrade to a patched version as specified in Fortinet's security advisory.

Fix this in Fortios Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2017-7739 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
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