# CVE-2018-0447: Cisco Email Security Appliance URL Filtering Bypass Vulnerability

> Remote attackers can bypass URL filtering on Cisco Email Security Appliances by sending crafted SPF packets, allowing malicious URLs to pass through.

- **Severity:** Medium 5.3 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/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:** No
- **Published:** 5 Oct 2018
- **Updated:** 26 Nov 2024
- **Also known as:** GHSA-6x9p-wvp8-hwgq

## What is CVE-2018-0447?

CVE-2018-0447 is a medium-severity vulnerability in Cisco Email Security Appliance, published on 5 Oct 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the anti-spam protection mechanisms of Cisco AsyncOS Software for the Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass certain content filters on an affected device. The vulnerability is due to incomplete input and validation checking mechanisms for certain Sender Policy Framework (SPF) messages that are sent to an affected device. An attacker could exploit this vulnerability by sending a customized SPF packet to an affected device. If successful, an exploit could allow the attacker to bypass the URL filters that are configured for the affected device, which could allow malicious URLs to pass through the device.

Weakness: CWE-20 (Improper Input Validation), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2018-0447?

It affects 1 product.


Products: Cisco Email Security Appliance.

## How do I fix CVE-2018-0447?

No fix has been published for CVE-2018-0447 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-0447 being exploited?

There is no known exploitation of CVE-2018-0447 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-2022-20960](https://insights.sbomify.com/CVE-2022-20960/): Denial of service in Cisco Secure Email (high 7.5)
- [CVE-2018-0419](https://insights.sbomify.com/CVE-2018-0419/): Security feature bypass in Email Security Appliance (ESA) (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0447 and fix it if it is affected.

What it is: CVE-2018-0447 is a medium-severity vulnerability in Cisco Email Security Appliance, published on 5 Oct 2018. 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-2018-0447 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-2018-0447/ (Markdown: https://insights.sbomify.com/CVE-2018-0447/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0447
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0447
- OSV: https://osv.dev/vulnerability/CVE-2018-0447

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From sbomify Insights: https://insights.sbomify.com/CVE-2018-0447/
Summaries are generated and may contain mistakes; the official description above is the record.