# CVE-2020-3596: Cisco Expressway Series and TelePresence Video Communication Server Denial of Service Vulnerability

> Unauthenticated remote attackers can cause a denial of service by sending crafted SIP packets to Cisco Expressway or VCS devices, exhausting memory and crashing the system.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** 8 Oct 2020
- **Updated:** 13 Nov 2024
- **Also known as:** GHSA-9c7p-6wrp-cw32

## What is CVE-2020-3596?

CVE-2020-3596 is a medium-severity denial of service vulnerability in Cisco TelePresence Video Communication Server (VCS) Expressway, published on 8 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Session Initiation Protocol (SIP) of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to incorrect handling of incoming SIP traffic. An attacker could exploit this vulnerability by sending a series of SIP packets to an affected device. A successful exploit could allow the attacker to exhaust memory on an affected device, causing it to crash and leading to a DoS condition.

Weakness: CWE-670 (Always-Incorrect Control Flow Implementation), CWE-789 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2020-3596?

It affects 2 products.


Products: Cisco Expressway, Cisco Telepresence Video Communication Server.

## How do I fix CVE-2020-3596?

No fix has been published for CVE-2020-3596 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3596 being exploited?

There is no known exploitation of CVE-2020-3596 in the wild and no public exploit code.

## Other vulnerabilities in Cisco TelePresence Video Communication Server (VCS) Expressway

- [CVE-2024-20252](https://insights.sbomify.com/CVE-2024-20252/): Cross-site request forgery in Cisco TelePresence Video Communication Server (VCS) Expressway (critical 9.6)
- [CVE-2024-20254](https://insights.sbomify.com/CVE-2024-20254/): Cross-site request forgery in Cisco TelePresence Video Communication Server (VCS) Expressway (critical 9.6)
- [CVE-2022-20812](https://insights.sbomify.com/CVE-2022-20812/): Cisco Expressway Series and Cisco TelePresence Video Communication Server Vulnerabilities (critical 9.0)
- [CVE-2022-20813](https://insights.sbomify.com/CVE-2022-20813/): Cisco Expressway Series and Cisco TelePresence Video Communication Server Vulnerabilities (critical 9.0)
- [CVE-2017-3790](https://insights.sbomify.com/CVE-2017-3790/): Denial of service in Cisco Expressway Series Software and Cisco TelePresence VCS Software All versions prior to version X8.8.2 are vulnerable (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3596 and fix it if it is affected.

What it is: CVE-2020-3596 is a medium-severity denial of service vulnerability in Cisco TelePresence Video Communication Server (VCS) Expressway, published on 8 Oct 2020. 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-2020-3596 in the wild and no public exploit code.

Affected product: Cisco TelePresence Video Communication Server (VCS) Expressway. 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-2020-3596/ (Markdown: https://insights.sbomify.com/CVE-2020-3596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3596
- OSV: https://osv.dev/vulnerability/CVE-2020-3596

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-3596/
Summaries are generated and may contain mistakes; the official description above is the record.