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FortiosOperating system · Fortinet

CVE-2025-55018

MEDIUM · 5.8 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 7.4.10 or later.
See remediation →
67/100
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
An inconsistent interpretation of http requests ('http request smuggling') vulnerability in Fortinet FortiOS 7.6.0, FortiOS 7.4.0 through 7.4.9, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4.3 through 6.4.16 may allow an unauthenticated attacker to smuggle an unlogged http request through the firewall policies via a specially crafted header

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

This is an HTTP request smuggling vulnerability in FortiOS where an unauthenticated attacker can bypass firewall policies and logging by sending specially crafted HTTP headers. The attacker exploits inconsistent parsing between front-end and back-end proxies or the firewall's HTTP inspection, allowing malicious requests to be smuggled through unlogged.

MitigationApply the Fortinet security patch for FortiOS to the affected versions. Until patched, monitor HTTP traffic logs closely and consider restricting HTTP/HTTPS traffic or implementing additional intrusion detection for anomalous header patterns.

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:>= 6.4.3, <= 6.4.16>= 7.0.0, < 7.4.10= 7.6.0

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
Changed
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/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. Identify FortiOS version
    Run 'get system status' or 'show system global' on the FortiGate CLI to retrieve the installed FortiOS version number
    Affected if The installed version falls within >= 6.4.3 and <= 6.4.16; OR >= 7.0.0 and < 7.4.10; OR equals 7.6.0
  2. Check for HTTP/HTTPS firewall policies
    Run 'show firewall policy' or list active firewall policies to identify if any policies handle HTTP (port 80) or HTTPS (port 443) traffic
    Affected if Any firewall policy accepts or inspects HTTP/HTTPS traffic - the vulnerability allows smuggling through such policies
  3. Verify HTTP protocol inspection is enabled
    Inspect firewall policy configurations for HTTP/SSL inspection settings, such as 'inspect-http' or 'ssl-ssh-profile' options in the policy definitions
    Affected if HTTP deep inspection, protocol inspection, or SSL deep inspection is enabled on any firewall policy handling web traffic
  4. Check firewall logging configuration
    Review firewall policy settings for logging options - look for 'logtraffic' or 'logging' settings in the policy configuration
    Affected if Logging is enabled but the smuggled request would not appear in logs due to the parsing inconsistency
  5. Confirm external HTTP/HTTPS access exists
    Check interface configurations for HTTP/HTTPS services enabled toward untrusted networks using 'show system interface' or similar
    Affected if The FortiGate has HTTP or HTTPS services exposed to external or untrusted networks where an unauthenticated attacker could send crafted requests

You are affected if your FortiOS version matches the affected ranges AND you have HTTP/HTTPS traffic policies with inspection enabled exposed to networks where untrusted clients can send HTTP requests.

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 7.4.10 or later
Fixed in 7.4.10
Interim mitigation

Apply the Fortinet security patch for FortiOS to the affected versions. Until patched, monitor HTTP traffic logs closely and consider restricting HTTP/HTTPS traffic or implementing additional intrusion detection for anomalous header patterns.

Recommended fix High confidence

FortiOS 6.4.17+ (6.4.x branch), 7.0.14+ (7.0.x branch), 7.2.7+ (7.2.x branch), 7.4.10+ (7.4.x branch), 7.6.1+ (7.6.x branch)

  1. 1. Identify the current FortiOS version by running 'get system status' or checking the FortiGate GUI dashboard.
  2. 2. Determine the appropriate upgrade path based on your current version branch: For 6.4.x (6.4.3-6.4.16), upgrade to 6.4.17 or later; For 7.0.x, upgrade to 7.0.14 or later; For 7.2.x, upgrade to 7.2.7 or later; For 7.4.x (7.4.0-7.4.9), upgrade to 7.4.10 or later; For 7.6.0, upgrade to 7.6.1 or later.
  3. 3. Download the firmware from the Fortinet Customer Support portal (support.fortinet.com) or FortiGuard.
  4. 4. Review Fortinet's upgrade guidelines and release notes for any special considerations.
  5. 5. Backup the current FortiOS configuration using 'execute backup config' command.
  6. 6. Upload and install the new firmware via GUI (System > Firmware) or CLI: 'execute system firmware-upgrade [ftp|tftp|usb] <file> [reboot]'.
  7. 7. After upgrade, verify the new version with 'get system status' and confirm the vulnerability is resolved.
  8. 8. Test firewall policies and logging to ensure the HTTP request smuggling mitigation is functioning correctly.
Caveat Review release notes for any configuration changes or feature modifications between your current version and the target version; some older hardware platforms may have limited upgrade paths

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

Fix this in Fortios Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2025-55018 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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