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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 10 Jul 2022. Known ransomware use
FortiproxyApplication · Fortinet

CVE-2018-13383

MEDIUM · 6.5 CVSS v3.1 Published 2019-05-29
Fix available
A fix is available. Upgrade to 1.2.9 / 5.2.15 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware 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
A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

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

A heap buffer overflow vulnerability in Fortinet FortiOS and FortiProxy SSL VPN web portal allows remote authenticated attackers to cause denial of service via specially crafted javascript href data when the web proxy handles webpages. The overflow occurs due to improper bounds checking when proxying webpage content.

MitigationUpgrade FortiOS to version 6.0.5 or later (or 5.6.11+, 5.4.13+, 5.2.15+), and FortiProxy to version 1.2.9+ or 2.0.1+ as applicable. Test SSL VPN functionality after upgrade.

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:< 1.2.9= 2.0.0
FortiosOperating system
Affected:>= 5.2.0, < 5.2.15>= 5.4.0, < 5.4.13>= 5.6.0, < 5.6.11>= 6.0.0, < 6.0.5

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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 and firmware version
    Access the FortiOS CLI and run 'get system status' or 'get version' to retrieve the firmware version. For FortiProxy, use 'get system status' or check the web UI under System > Firmware.
    Affected if The version falls within FortiOS 5.2.0-5.2.14, 5.4.0-5.4.12, 5.6.0-5.6.10, 6.0.0-6.0.4 OR FortiProxy versions below 1.2.9 or exactly 2.0.0
  2. Confirm SSL VPN web portal is enabled
    In FortiOS web UI, navigate to VPN > SSL-VPN Settings, or in CLI run 'show ssl-vpn settings'. For FortiProxy, check under Proxy Settings > Explicit Proxy > SSL-VPN.
    Affected if SSL VPN web portal or web proxy feature is enabled and accessible to users
  3. Verify remote authentication is permitted for SSL VPN
    In FortiOS CLI, run 'show ssl-vpn setting' and check authentication groups under 'set auth-group'. In web UI, review VPN > SSL-VPN > Authentication/Portal mapping settings.
    Affected if Remote users (without VPN client) can authenticate to the SSL VPN portal, allowing them to submit the specially crafted javascript href data
  4. Check web proxy handling of external webpages
    Review proxy configuration via 'show web-proxy' or check Explicit Proxy settings in FortiProxy. Look for proxying of webpage content enabled.
    Affected if The SSL VPN web proxy is configured to handle and proxy external webpage content to authenticated users

You are affected if your FortiOS or FortiProxy version is within the vulnerable ranges AND SSL VPN web portal with remote authentication and web proxy content handling is enabled.

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 1.2.9 / 5.2.15 / 5.4.13 or later
Fixed in 1.2.95.2.155.4.13
Interim mitigation

Upgrade FortiOS to version 6.0.5 or later (or 5.6.11+, 5.4.13+, 5.2.15+), and FortiProxy to version 1.2.9+ or 2.0.1+ as applicable. Test SSL VPN functionality after upgrade.

Recommended fix High confidence

FortiOS: 5.2.15+, 5.4.13+, 5.6.11+, 6.0.5+ | FortiProxy: 1.2.9+, 2.0.1+

  1. 1. Identify the current FortiOS or FortiProxy version by logging into the device CLI and running 'get system status' or checking the web UI dashboard.
  2. 2. For FortiOS 5.2.x users: Upgrade to FortiOS 5.2.15 or later.
  3. 3. For FortiOS 5.4.x users: Upgrade to FortiOS 5.4.13 or later.
  4. 4. For FortiOS 5.6.x users: Upgrade to FortiOS 5.6.11 or later.
  5. 5. For FortiOS 6.0.x users: Upgrade to FortiOS 6.0.5 or later.
  6. 6. For FortiProxy 1.2.x users: Upgrade to FortiProxy 1.2.9 or later.
  7. 7. For FortiProxy 2.0.0 users: Upgrade to FortiProxy 2.0.1 or later.
  8. 8. Download the firmware from Fortinet's support portal (support.fortinet.com) and upload via the FortiGate/FortiProxy web UI under System > Firmware or via CLI using 'execute firmware upgrade'.
Caveat Major version upgrades (e.g., 5.4 to 5.6, 5.6 to 6.0) may have configuration or feature changes - review Fortinet release notes and test in staging first

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

Fix this in Fortiproxy Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing6.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,600
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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-2018-13383 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