# CVE-2018-20809: Denial of service in n/a

> A crafted message can crash the Pulse Secure Pulse Connect Secure web server, causing a denial of service for administrators and users.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Mar 2019
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-x2mw-2wgh-5r92

## What is CVE-2018-20809?

CVE-2018-20809 is a high-severity denial of service vulnerability in Ivanti Connect Secure, published on 16 Mar 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A crafted message can cause the web server to crash with Pulse Secure Pulse Connect Secure (PCS) 8.3RX before 8.3R5 and Pulse Policy Secure 5.4RX before 5.4R5. This is not applicable to PCS 8.1RX.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2018-20809?

It affects 2 products.


Products: Ivanti Connect Secure, Pulsesecure Pulse Policy Secure.

## How do I fix CVE-2018-20809?

No fix has been published for CVE-2018-20809 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-20809 being exploited?

There is no known exploitation of CVE-2018-20809 in the wild and no public exploit code.

## Other vulnerabilities in Ivanti Connect Secure

- [CVE-2021-22893](https://insights.sbomify.com/CVE-2021-22893/): Ivanti Pulse Connect Secure Use-After-Free (critical 10.0, exploited in the wild)
- [CVE-2019-11510](https://insights.sbomify.com/CVE-2019-11510/): Ivanti Pulse Connect Secure Arbitrary File Read (critical 9.9, exploited in the wild)
- [CVE-2024-21887](https://insights.sbomify.com/CVE-2024-21887/): Ivanti Connect Secure and Policy Secure Command Injection (critical 9.1, exploited in the wild)
- [CVE-2025-22457](https://insights.sbomify.com/CVE-2025-22457/): Ivanti Connect Secure, Policy Secure, and ZTA Gateways Stack-Based Buffer Overflow (critical 9.0, exploited in the wild)
- [CVE-2025-0282](https://insights.sbomify.com/CVE-2025-0282/): Ivanti Connect Secure, Policy Secure, and ZTA Gateways Stack-Based Buffer Overflow (critical 9.0, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-20809 and fix it if it is affected.

What it is: CVE-2018-20809 is a high-severity denial of service vulnerability in Ivanti Connect Secure, published on 16 Mar 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-20809 in the wild and no public exploit code.

Affected product: Ivanti Connect Secure. 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-2018-20809/ (Markdown: https://insights.sbomify.com/CVE-2018-20809/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20809
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20809
- OSV: https://osv.dev/vulnerability/CVE-2018-20809

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20809/
Summaries are generated and may contain mistakes; the official description above is the record.