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Fortios Ips EngineApplication · Fortinet

CVE-2023-40718

HIGH · 7.5 CVSS v3.1 Published 2023-10-10
Fix available
A fix is available. Upgrade to after 7.312 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
A interpretation conflict in Fortinet IPS Engine versions 7.321, 7.166 and 6.158 allows attacker to evade IPS features via crafted TCP packets.

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

Fortinet IPS Engine versions 7.321, 7.166, and 6.158 contain an interpretation conflict vulnerability in how the engine processes crafted TCP packets. An attacker can exploit this by sending specially constructed TCP packets that cause the IPS to misinterpret the traffic, effectively bypassing IPS detection and inspection features.

MitigationUpdate Fortinet IPS Engine to the latest patched version available from Fortinet's support portal. Prioritize updates for devices with direct internet exposure or those serving as perimeter security controls.

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
Fortios Ips EngineApplication
Affected:<= 7.312<= 7.165<= 6.158

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:3.1/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 installed Fortinet IPS Engine version
    Run command: `get system ips` or `diagnose ips version` on Fortinet device CLI. Alternatively, check FortiView or System > FortiGuard page for IPS engine version.
    Affected if Version is 7.312 or lower for 7.x branch, 7.165 or lower for 7.1xx branch, or any 6.158 and below.
  2. Confirm IPS inspection is enabled
    Run `get system ips` or check GUI: Security Profiles > Intrusion Prevention. Verify 'inspect' or 'enable' status is active.
    Affected if IPS inspection profile is applied to a policy and the IPS engine is actively inspecting traffic.
  3. Check if IPS is applied to firewall policy
    Run `get firewall policy` and look for policies with 'ips-sensor' or 'IPS' profile enabled. Also check `diagnose system ips status`.
    Affected if Any policy has an IPS sensor attached and is processing traffic.
  4. Verify TCP traffic inspection is active
    Check IPS sensor configuration via CLI: `get ips sensor [sensor_name]` and confirm 'protocol` and 'tcp' options are not set to 'disable'.
    Affected if TCP protocol inspection is enabled within the active IPS sensor profile.

User is affected if the installed IPS engine version falls within the vulnerable ranges (<=7.312, <=7.165, <=6.158) AND IPS inspection with TCP handling is actively applied to firewall policies.

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 a release after 7.312
Interim mitigation

Update Fortinet IPS Engine to the latest patched version available from Fortinet's support portal. Prioritize updates for devices with direct internet exposure or those serving as perimeter security controls.

Recommended fix Moderate confidence

FortiOS 7.4.x (contains IPS engine 7.322 or later) or FortiOS 7.2.x or later, or FortiOS 6.4.15 or later depending on your current branch

  1. 1. Identify the current FortiOS version by running: get system status or diag -q | grep version
  2. 2. Determine the IPS engine version by running: diagnose ips engine list
  3. 3. Based on the current FortiOS branch, plan the upgrade: For 7.3.x branch, upgrade to version 7.4.0 or later (which includes IPS engine 7.322 or later); For 7.1.x branch, upgrade to version 7.2.0 or later; For 6.0.x branch, upgrade to version 6.4.15 or later
  4. 4. Download the firmware upgrade from Fortinet's support portal: https://support.fortinet.com/
  5. 5. Upload the firmware to the FortiGate device via GUI (System > Firmware) or CLI: execute restore image tftp <filename> <tftp-server>
  6. 6. Verify the upgrade completed successfully and the IPS engine version has updated: diagnose ips engine list
  7. 7. Confirm the vulnerability is resolved by checking the IPS signature version: diagnose ips sig version
Caveat Review FortiOS release notes for your target version for any configuration or behavioral changes; test upgrade in staging environment first

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

Fix this in Fortios Ips Engine Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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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-2023-40718 in production — separate from our analysis above.

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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