Policy bypass via crafted HTTP header smuggling
Published Feb 10, 2026 · Updated Feb 10, 2026
HTTP request smuggling in affected Fortinet FortiOS releases allows remote attackers to bypass firewall policies with an unlogged request. FortiOS interprets a specially crafted HTTP header inconsistently while enforcing firewall policy, allowing a smuggled request to pass without being logged; Fortinet has not disclosed the exact header syntax or parser branch. No authentication or user interaction is required, and the reported consequence is limited to policy bypass and request concealment rather than code execution or service interruption.
Summary
What happened
HTTP request smuggling in affected Fortinet FortiOS releases allows remote attackers to bypass firewall policies with an unlogged request. FortiOS interprets a specially crafted HTTP header inconsistently while enforcing firewall policy, allowing a smuggled request to pass without being logged; Fortinet has not disclosed the exact header syntax or parser branch. No authentication or user interaction is required, and the reported consequence is limited to policy bypass and request concealment rather than code execution or service interruption.
The record
- CVE
- CVE-2025-55018
- Published
- Feb 10, 2026
- Updated
- Feb 10, 2026
- Vendor
- Fortinet
- Product
- FortiOS
- Classifications
- CWE-444, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 10, 2026CVE publishedPublication date reported by the CVE source.
- Feb 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=6.4.3 <=6.4.16
- Affected versionversion=7.0.0 <=7.0.19
- Affected versionversion=7.2.0 <=7.2.13
- Affected versionversion=7.4.0 <=7.4.9
- Affected versionversion=7.6.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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