# CVE-2022-20960: Denial of service in Cisco Secure Email

> Unauthenticated remote attackers can cause a denial of service on Cisco Email Security Appliances by exhausting resources with concurrent TLS connections.

- **Severity:** High 7.5 (`CVSS:3.1/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:** 3 Nov 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-m7jq-xvr4-f7xc

## What is CVE-2022-20960?

CVE-2022-20960 is a high-severity denial of service vulnerability in Cisco Email Security Appliance, published on 3 Nov 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated remote attacker to cause a denial of service (DoS) condition on an affected device.

 This vulnerability is due to improper handling of certain TLS connections that are processed by an affected device. An attacker could exploit this vulnerability by establishing a large number of concurrent TLS connections to an affected device. A successful exploit could allow the attacker to cause the device to drop new TLS email messages that come from the associated email servers. Exploitation of this vulnerability does not cause the affected device to unexpectedly reload. The device will recover autonomously within a few hours of when the attack is halted or mitigated.

Weakness: CWE-295 (Improper Certificate Validation), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2022-20960?

It affects 1 product.


Products: Cisco Email Security Appliance.

## How do I fix CVE-2022-20960?

No fix has been published for CVE-2022-20960 yet. Limit exposure of the affected software until one is available.

## Is CVE-2022-20960 being exploited?

There is no known exploitation of CVE-2022-20960 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Email Security Appliance

- [CVE-2022-20798](https://insights.sbomify.com/CVE-2022-20798/): Cisco Email Security Appliance and Cisco Secure Email and Web Manager External Authentication Bypass Vulnerability (critical 9.8)
- [CVE-2015-6291](https://insights.sbomify.com/CVE-2015-6291/): Denial of service in n/a (high 7.8)
- [CVE-2022-20664](https://insights.sbomify.com/CVE-2022-20664/): Cisco Email Security Appliance and Cisco Secure Email and Web Manager Information Disclosure Vulnerability (high 7.7)
- [CVE-2018-0419](https://insights.sbomify.com/CVE-2018-0419/): Security feature bypass in Email Security Appliance (ESA) (high 7.5)
- [CVE-2016-1480](https://insights.sbomify.com/CVE-2016-1480/): Security feature bypass in Cisco AsyncOS through WSA10.0.0-000 (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-20960 and fix it if it is affected.

What it is: CVE-2022-20960 is a high-severity denial of service vulnerability in Cisco Email Security Appliance, published on 3 Nov 2022. 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-2022-20960 in the wild and no public exploit code.

Affected product: Cisco Email Security Appliance. 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-2022-20960/ (Markdown: https://insights.sbomify.com/CVE-2022-20960/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-20960
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-20960
- OSV: https://osv.dev/vulnerability/CVE-2022-20960

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-20960/
Summaries are generated and may contain mistakes; the official description above is the record.