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FortiproxyApplication · Fortinet

CVE-2021-26092

MEDIUM · 6.1 CVSS v3.1 Published 2022-02-24
Fix available
A fix is available. Upgrade to after 6.4.4 or later.
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
Failure to sanitize input in the SSL VPN web portal of FortiOS 5.2.10 through 5.2.15, 5.4.0 through 5.4.13, 5.6.0 through 5.6.14, 6.0.0 through 6.0.12, 6.2.0 through 6.2.7, 6.4.0 through 6.4.4; and FortiProxy 1.2.0 through 1.2.9, 2.0.0 through 2.0.1 may allow a remote unauthenticated attacker to perform a reflected Cross-site Scripting (XSS) attack by sending a request to the error page with malicious GET parameters.

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 Cross-Site Scripting (XSS) vulnerability in the SSL VPN web portal of FortiOS and FortiProxy allows remote unauthenticated attackers to inject malicious JavaScript via unsanitized GET parameters submitted to the error page.

MitigationApply the vendor-supplied patches by upgrading FortiOS to version 5.2.16+, 5.4.14+, 5.6.15+, 6.0.13+, 6.2.8+, 6.4.5+ and FortiProxy to version 1.2.10+ or 2.0.2+ as specified in the Fortinet 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
FortiproxyApplication
Affected:>= 1.2.0, <= 1.2.9= 2.0.0= 2.0.1
FortiosOperating system
Affected:>= 5.2.10, <= 5.2.15>= 5.4.0, <= 5.4.13>= 5.6.0, <= 5.6.14>= 6.0.0, <= 6.0.12>= 6.2.0, <= 6.2.7>= 6.4.0, <= 6.4.4

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:3.1/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. Identify the product type
    Run 'get system status' via FortiOS/FortiProxy CLI or check the device model via web UI. FortiProxy devices will show as 'FortiProxy' in the model field.
    Affected if The device is a FortiOS or FortiProxy appliance
  2. Determine the firmware version
    Run 'get system status' via CLI. The output displays the firmware version (for example: FortiOS v6.0.12 or FortiProxy v2.0.1).
    Affected if The version falls within the affected ranges: FortiProxy 1.2.0-1.2.9, 2.0.0-2.0.1; FortiOS 5.2.10-5.2.15, 5.4.0-5.4.13, 5.6.0-5.6.14, 6.0.0-6.0.12, 6.2.0-6.2.7, or 6.4.0-6.4.4
  3. Verify SSL VPN web portal is enabled
    Run 'get vpn ssl settings' via CLI. Look for 'set ssl-port' (typically 443) and confirm the service is active. Alternatively, check via web UI under VPN > SSL-VPN Settings.
    Affected if The SSL VPN web portal is enabled and accessible (ssl-port is configured and status is active)
  4. Confirm the SSL VPN portal is externally accessible
    Attempt to reach the SSL VPN login page externally via the public IP or hostname on the configured SSL port (usually 443). The vulnerability exists on the error page triggered by malformed GET parameters.
    Affected if The SSL VPN portal is reachable from untrusted networks (internet-facing)

A user is affected if they run an unpatched FortiOS or FortiProxy version within the affected ranges AND have the SSL VPN web portal enabled and accessible.

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 6.4.4
Interim mitigation

Apply the vendor-supplied patches by upgrading FortiOS to version 5.2.16+, 5.4.14+, 5.6.15+, 6.0.13+, 6.2.8+, 6.4.5+ and FortiProxy to version 1.2.10+ or 2.0.2+ as specified in the Fortinet security advisory.

Recommended fix High confidence

FortiOS: 5.2.16+, 5.4.14+, 5.6.15+, 6.0.13+, 6.2.8+, 6.4.5+ | FortiProxy: 1.2.10+, 2.0.2+

  1. 1. Identify the currently installed FortiOS or FortiProxy version using the web UI or CLI command 'get system status'
  2. 2. For FortiOS 5.2.x: Upgrade to version 5.2.16 or later
  3. 3. For FortiOS 5.4.x: Upgrade to version 5.4.14 or later
  4. 4. For FortiOS 5.6.x: Upgrade to version 5.6.15 or later
  5. 5. For FortiOS 6.0.x: Upgrade to version 6.0.13 or later
  6. 6. For FortiOS 6.2.x: Upgrade to version 6.2.8 or later
  7. 7. For FortiOS 6.4.x: Upgrade to version 6.4.5 or later
  8. 8. For FortiProxy 1.2.x: Upgrade to version 1.2.10 or later
Caveat Review release notes for your specific version upgrade path; some upgrades may require intermediate steps for major version jumps

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

Fix this in Fortiproxy Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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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-2021-26092 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