# CVE-2017-3818: Security feature bypass in Cisco AsyncOS 9.7.1-066

> Remote attackers can bypass email filters on Cisco ESA devices by exploiting a MIME scanner flaw, requiring specific filter configurations.

- **Severity:** Medium 5.8 (`CVSS:3.0/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:** No
- **Published:** 3 Feb 2017
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-hhrh-pc24-4cm9

## What is CVE-2017-3818?

CVE-2017-3818 is a medium-severity vulnerability in Cisco AsyncOS 9.7.1-066, published on 3 Feb 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Multipurpose Internet Mail Extensions (MIME) scanner of Cisco AsyncOS Software for Cisco Email Security Appliances (ESA) could allow an unauthenticated, remote attacker to bypass configured user filters on the device, aka a Malformed MIME Header Filtering Bypass. This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco Email Security Appliances, both virtual and hardware appliances, if the software is configured to apply a message filter or content filter to incoming email attachments. More Information: CSCvb65245. Known Affected Releases: 9.7.1-066. Known Fixed Releases: 9.8.0-092.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2017-3818?

It affects 1 product.


Products: Cisco Email Security Appliance Firmware.

## How do I fix CVE-2017-3818?

No fix has been published for CVE-2017-3818 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-3818 being exploited?

There is no known exploitation of CVE-2017-3818 in the wild and no public exploit code.

## Other vulnerabilities in Cisco AsyncOS 9.7.1-066

- [CVE-2016-6406](https://insights.sbomify.com/CVE-2016-6406/): Auth bypass in n/a (critical 9.8)
- [CVE-2018-15453](https://insights.sbomify.com/CVE-2018-15453/): Cisco Email Security Appliance Memory Corruption Denial of Service Vulnerability (high 8.6)
- [CVE-2017-6671](https://insights.sbomify.com/CVE-2017-6671/): Security feature bypass in Cisco Email Security Appliance (high 7.5)
- [CVE-2016-6458](https://insights.sbomify.com/CVE-2016-6458/): Security feature bypass in Cisco AsyncOS 10.0.0-125 and 9.7.1-066 (high 7.5)
- [CVE-2019-12706](https://insights.sbomify.com/CVE-2019-12706/): Cisco Email Security Appliance Filter Bypass Vulnerability (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-3818 and fix it if it is affected.

What it is: CVE-2017-3818 is a medium-severity vulnerability in Cisco AsyncOS 9.7.1-066, published on 3 Feb 2017. 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-2017-3818 in the wild and no public exploit code.

Affected product: Cisco AsyncOS 9.7.1-066. 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-2017-3818/ (Markdown: https://insights.sbomify.com/CVE-2017-3818/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-3818
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-3818
- OSV: https://osv.dev/vulnerability/CVE-2017-3818

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-3818/
Summaries are generated and may contain mistakes; the official description above is the record.