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FortiosOperating system · Fortinet

CVE-2016-7541

MEDIUM · 5.9 CVSS v3.0 Published 2017-03-30
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 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
Long lived sessions in Fortinet FortiGate devices with FortiOS 5.x before 5.4.0 could violate a security policy during IPS signature updates when the FortiGate's IPSengine is configured in flow mode. All FortiGate versions with IPS configured in proxy mode (the default mode) are not affected.

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 · moderate confidence

FortiGate devices running FortiOS 5.x before 5.4.0 with IPS engine configured in flow mode (non-default) allow long-lived sessions to violate security policies during IPS signature updates. This occurs because sessions established before a signature update may not receive the new security policy enforcement, creating a window where threats can pass unchecked.

MitigationUpdate FortiOS to version 5.4.0 or later, or configure IPS to use proxy mode (the default setting) instead of flow mode.

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:= 5.0.0= 5.0.1= 5.0.2= 5.0.3= 5.0.4= 5.0.5= 5.0.6= 5.0.7= 5.0.8= 5.0.9= 5.0.10= 5.0.11

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.0/AV:N/AC:H/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. Check FortiOS version
    Run 'get system status' or 'fnsysctl cat /proc/version' to display the firmware version
    Affected if Version is 5.0.0 through 5.0.11 (versions before 5.4.0)
  2. Verify IPS engine mode configuration
    Run 'get ips global' or 'config ips global' then 'show' to display IPS engine settings
    Affected if IPS is set to flow-based inspection mode (flow-mode) rather than proxy mode
  3. Identify active sessions
    Run 'get session list' or 'diag session list' to display current active sessions and their duration
    Affected if Long-lived sessions exist that were established before recent IPS signature updates

Environment is affected if FortiOS version is between 5.0.0-5.0.11 AND IPS is configured in flow mode AND there are active long-lived sessions present

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

Update FortiOS to version 5.4.0 or later, or configure IPS to use proxy mode (the default setting) instead of flow mode.

Fix this in Fortios Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2016-7541 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