# CVE-2026-20057: Cisco Secure Firewall Threat Defense Software Snort 3 Visual Basic for Application Denial of Service Vulnerability

> Remote attackers can crash the Snort 3 Detection Engine by sending crafted VBA data, causing a denial of service on Cisco firewall products.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Mar 2026
- **Updated:** 4 Mar 2026
- **Also known as:** GHSA-3fxq-cwj2-m4x3

## What is CVE-2026-20057?

CVE-2026-20057 is a medium-severity denial of service vulnerability in Cisco Secure Firewall Threat Defense, published on 4 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Multiple Cisco products are affected by a vulnerability in the Snort 3 Visual Basic for Applications (VBA) feature which could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to crash. 
 
This vulnerability is due to lack of proper error checking when decompressing VBA data. An attacker could exploit this vulnerability by sending a crafted VBA data to the Snort 3 Detection Engine on the targeted device. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to unexpectedly restart causing a a denial of service (DoS) condition.

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2026-20057?

It affects 4 products.


Products: Cisco Cyber Vision, Cisco Secure Firewall Threat Defense, Cisco Snort, Cisco Unified Threat Defense Snort Intrusion Prevention System Engine.

## How do I fix CVE-2026-20057?

No fix has been published for CVE-2026-20057 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20057 being exploited?

There is no known exploitation of CVE-2026-20057 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Secure Firewall Threat Defense

- [CVE-2022-20685](https://insights.sbomify.com/CVE-2022-20685/): Multiple Cisco Products Snort Modbus Denial of Service Vulnerability (high 7.5)
- [CVE-2026-20005](https://insights.sbomify.com/CVE-2026-20005/): Denial of service in Cisco Cyber Vision (medium 5.8)
- [CVE-2026-20053](https://insights.sbomify.com/CVE-2026-20053/): Memory corruption in Cisco Cyber Vision (medium 5.8)
- [CVE-2026-20054](https://insights.sbomify.com/CVE-2026-20054/): Denial of service in Cisco Cyber Vision (medium 5.8)
- [CVE-2026-20067](https://insights.sbomify.com/CVE-2026-20067/): Multiple Cisco Products Snort 3 TBD Denial of Service Vulnerability (medium 5.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20057 and fix it if it is affected.

What it is: CVE-2026-20057 is a medium-severity denial of service vulnerability in Cisco Secure Firewall Threat Defense, published on 4 Mar 2026. 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-2026-20057 in the wild and no public exploit code.

Affected product: Cisco Secure Firewall Threat Defense. 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-2026-20057/ (Markdown: https://insights.sbomify.com/CVE-2026-20057/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20057
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20057
- OSV: https://osv.dev/vulnerability/CVE-2026-20057

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-20057/
Summaries are generated and may contain mistakes; the official description above is the record.