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Weekly Signal
Live intelligence Updated 21 Aug 2026 · 22:11 UTC

Fortinet · FortiOS, FortiOS and FortiProxy, Fortiproxy

CVE-2018-13383

Fortinet FortiOS and FortiProxy Out-of-bounds Write

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Vendor advisory from fortiguard.com

View response plan
CVSS6.5
EPSS33.6%
KEVYes
ExploitationConfirmed exploitation
RemediationNot yet verified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 33.6%; technical severity is CVSS 6.5.

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.

Who should care

  • Teams operating FortiOS, FortiOS and FortiProxy, Fortiproxy
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether FortiOS, FortiOS and FortiProxy, Fortiproxy is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Vendor advisory from fortiguard.com
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Required Action

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CWE
CWE-787
Affected versions
Fortinet FortiOS (Start Including 5.2.0, End Excluding 5.2.15 | Start Including 5.4.0, End Excluding 5.4.13 | Start Including 5.6.0, End Excluding 5.6.11 | Start Including 6.0.0, End Excluding 6.0.5); Fortinet FortiOS and FortiProxy; Fortinet Fortiproxy (End Excluding 1.2.9 | Version 2.0.0)
Fixed versions
Fortinet FortiOS (Fixed from 5.2.15, 5.4.13, 5.6.11, 6.0.5); Fortinet Fortiproxy (Fixed from 1.2.9)
Published
29 May 2019
Attack vector
Network
Privileges required
None
User interaction
Required

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 33.6%
  4. Signal calculated at 76

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.