# CVE-2026-20290: Cisco Secure Firewall Threat Defense Software Snort 2 SSL/TLS Denial of Service Vulnerability

> An unauthenticated remote attacker can cause a denial of service by sending a crafted SSL connection request to the Snort 2 Detection Engine.

- **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:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-xxfc-5fpg-3fhq

## What is CVE-2026-20290?

CVE-2026-20290 is a medium-severity denial of service vulnerability in Cisco Secure Firewall Threat Defense (FTD) Software, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in SSL/TLS certificate parsing in the Snort 2 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 2 Detection Engine to restart.

This vulnerability is due to incomplete validation of the SSL certificate. An attacker could exploit this vulnerability by sending a crafted SSL connection setup request to be parsed by Snort 2. A successful exploit could allow the attacker to cause the Snort 2 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition.

Weakness: CWE-805 (Buffer Access with Incorrect Length Value)

## Which versions are affected by CVE-2026-20290?


## How do I fix CVE-2026-20290?

No fix has been published for CVE-2026-20290 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20290 being exploited?

There is no known exploitation of CVE-2026-20290 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20290 and fix it if it is affected.

What it is: CVE-2026-20290 is a medium-severity denial of service vulnerability in Cisco Secure Firewall Threat Defense (FTD) Software, published on 16 Sep 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-2026-20290 in the wild and no public exploit code.

Affected product: Cisco Secure Firewall Threat Defense (FTD) Software. 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-2026-20290/ (Markdown: https://insights.sbomify.com/CVE-2026-20290/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20290
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20290
- OSV: https://osv.dev/vulnerability/CVE-2026-20290

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-20290/
Summaries are generated and may contain mistakes; the official description above is the record.