# CVE-2021-1224: Multiple Cisco Products Snort TCP Fast Open File Policy Bypass Vulnerability

> Unauthenticated remote attackers can bypass HTTP file policies on Cisco Firepower devices by exploiting TCP Fast Open handling in the Snort engine.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Jan 2021
- **Updated:** 12 Nov 2024
- **Also known as:** GHSA-p854-c355-26cj, UBUNTU-CVE-2021-1224

## What is CVE-2021-1224?

CVE-2021-1224 is a medium-severity vulnerability in Cisco Ios Xe, published on 13 Jan 2021. 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 with TCP Fast Open (TFO) when used in conjunction with the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured file policy for HTTP. The vulnerability is due to incorrect detection of the HTTP payload if it is contained at least partially within the TFO connection handshake. An attacker could exploit this vulnerability by sending crafted TFO packets with an HTTP payload through an affected device. A successful exploit could allow the attacker to bypass configured file policy for HTTP packets and deliver a malicious payload.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2021-1224?

It affects 16 products.


Products: Cisco Ios Xe, Cisco Meraki Mx100 Firmware, Cisco Meraki Mx250 Firmware, Cisco Meraki Mx450 Firmware, Cisco Meraki Mx64 Firmware, Cisco Meraki Mx64w Firmware, Cisco Meraki Mx67 Firmware, Cisco Meraki Mx67c Firmware, Cisco Meraki Mx67w Firmware, Cisco Meraki Mx68 Firmware, Cisco Meraki Mx68cw Firmware, Cisco Meraki Mx68w Firmware, Cisco Meraki Mx84 Firmware, Cisco Secure Firewall Management Center, Cisco Secure Firewall Threat Defense, Snort Snort.

## How do I fix CVE-2021-1224?

Apply the vendor's patch.

## Is CVE-2021-1224 being exploited?

There is no known exploitation of CVE-2021-1224 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xe

- [CVE-2023-20198](https://insights.sbomify.com/CVE-2023-20198/): Cisco IOS XE Web UI Privilege Escalation (critical 10.0, exploited in the wild)
- [CVE-2018-0151](https://insights.sbomify.com/CVE-2018-0151/): Cisco IOS Software and Cisco IOS XE Software Quality of Service Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2023-20273](https://insights.sbomify.com/CVE-2023-20273/): Cisco IOS XE Web UI Command Injection (high 7.2, exploited in the wild)
- [CVE-2025-20188](https://insights.sbomify.com/CVE-2025-20188/): Hardcoded credentials in Cisco IOS XE Software (critical 10.0)
- [CVE-2021-34770](https://insights.sbomify.com/CVE-2021-34770/): Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers CAPWAP Remote Code Execution Vulnerability (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1224 and fix it if it is affected.

What it is: CVE-2021-1224 is a medium-severity vulnerability in Cisco Ios Xe, published on 13 Jan 2021. 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-2021-1224 in the wild and no public exploit code.

Affected product: Cisco Ios Xe. 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-2021-1224/ (Markdown: https://insights.sbomify.com/CVE-2021-1224/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1224
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1224
- OSV: https://osv.dev/vulnerability/CVE-2021-1224

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1224/
Summaries are generated and may contain mistakes; the official description above is the record.