# CVE-2018-13383: Fortinet FortiOS and FortiProxy Out-of-bounds Write

> Heap buffer overflow in FortiOS SSL VPN web portal causes service termination for logged-in users due to improper handling of JavaScript href data.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Yes, since 10 Jan 2022 (CISA KEV), used in ransomware
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 May 2019
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-cjc8-2cq5-7jq7

## What is CVE-2018-13383?

CVE-2018-13383 is a medium-severity memory corruption vulnerability in Fortinet Fortios, published on 29 May 2019. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2018-13383?

It affects 2 products.


Products: Fortinet Fortios, Fortinet Fortiproxy.

## How do I fix CVE-2018-13383?

No fix has been published for CVE-2018-13383 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 10 Jul 2022.

## Is CVE-2018-13383 being exploited?

Yes. Attackers have exploited CVE-2018-13383 in the wild since at least 10 Jan 2022, including in ransomware campaigns.

## Other vulnerabilities in Fortinet Fortios

- [CVE-2024-23113](https://insights.sbomify.com/CVE-2024-23113/): Fortinet Multiple Products Format String (critical 9.8, exploited in the wild)
- [CVE-2022-40684](https://insights.sbomify.com/CVE-2022-40684/): Fortinet Multiple Products Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2024-55591](https://insights.sbomify.com/CVE-2024-55591/): Fortinet FortiOS and FortiProxy Authentication Bypass (critical 9.6, exploited in the wild)
- [CVE-2024-21762](https://insights.sbomify.com/CVE-2024-21762/): Fortinet FortiOS Out-of-Bound Write (critical 9.6, exploited in the wild)
- [CVE-2022-42475](https://insights.sbomify.com/CVE-2022-42475/): Fortinet FortiOS Heap-Based Buffer Overflow (critical 9.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-13383 and fix it if it is affected.

What it is: CVE-2018-13383 is a medium-severity memory corruption vulnerability in Fortinet Fortios, published on 29 May 2019. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2018-13383 in the wild since at least 10 Jan 2022, including in ransomware campaigns.

Affected product: Fortinet Fortios. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-13383/ (Markdown: https://insights.sbomify.com/CVE-2018-13383/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-13383
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-13383
- OSV: https://osv.dev/vulnerability/CVE-2018-13383

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-13383/
Summaries are generated and may contain mistakes; the official description above is the record.