Secuno
ENNL
Book demo

CVE-2018-13383

Fortinet FortiOS and FortiProxy Out-of-bounds Write

4.3 MEDIUMActively exploited (CISA KEV)Used in ransomwareEPSS 33.6%
  1. Published29 May 2019
  2. Added to CISA KEV10 Jan 2022
  3. Remediation due10 Jul 2022
Actively exploited (CISA KEV)

A heap buffer overflow in Fortinet FortiOS and FortiProxy may cause the SSL VPN web service termination for logged in users.

Added to KEV: 10 Jan 2022Federal remediation due: 10 Jul 2022Used in ransomware

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Affected products

Fortinet FortiProxy< 1.2.9 · 2.0.0
Fortinet FortiOS≥ 5.2.0 < 5.2.15 · ≥ 5.4.0 < 5.4.13 · ≥ 5.6.0 < 5.6.11 · ≥ 6.0.0 < 6.0.5

Remediation

Fixed in
Fortinet FortiProxy≥ 1.2.9
Fortinet FortiOS≥ 5.2.15

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-1078158.5
MariaDB server is a community developed fork of MySQL server. From 10.6.1 until…
CVE-2026-195708.8
The LE Audio Broadcast Sink in subsys/bluetooth/audio/bap_broadcast_sink.c copies…
CVE-2026-1079099.1
A heap-based out-of-bounds write in the ws_read_frame function (src/bolt/ws.c) and the…
CVE-2026-1079089.8
A heap-based out-of-bounds write in the BoltReadHandler function (src/bolt/bolt_api.c)…
CVE-2026-823448.1
IBM Guardium Data Protection 12.0, 12.1 is vulnerable to a heap-based buffer overflow…
CVE-2026-823358.1
IBM Guardium Data Protection 12.0, 12.1, 12.2 is vulnerable to a heap-based buffer…

Frequently asked

Is CVE-2018-13383 being actively exploited?

Yes. CVE-2018-13383 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 10 Jan 2022. It has been used in ransomware campaigns.

How severe is CVE-2018-13383?

CVE-2018-13383 has a CVSS 3.1 base score of 4.3, rated medium. EPSS estimates a 33.6% probability of exploitation.

Which products are affected by CVE-2018-13383?

Affected products include Fortinet FortiProxy, Fortinet FortiOS.

How do I fix CVE-2018-13383?

Upgrade affected software to a fixed version, for example Fortinet FortiProxy 1.2.9, Fortinet FortiOS 5.2.15 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2018-13383 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.