# CVE-2019-1921: Cisco Email Security Appliance Content Filter Bypass Vulnerability

> Remote attackers can bypass email content filters by naming malicious attachments with specific patterns, allowing blocked files to pass through.

- **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:** 6 Jul 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-q86h-wvjc-7wh4

## What is CVE-2019-1921?

CVE-2019-1921 is a medium-severity vulnerability in Cisco Email Security Appliance, published on 6 Jul 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the attachment scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured content filters on the device. The vulnerability is due to improper input validation of the email body. An attacker could exploit this vulnerability by naming a malicious attachment with a specific pattern. A successful exploit could allow the attacker to bypass configured content filters that would normally block the attachment.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-1921?

It affects 1 product.


Products: Cisco Email Security Appliance.

## How do I fix CVE-2019-1921?

No fix has been published for CVE-2019-1921 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1921 being exploited?

There is no known exploitation of CVE-2019-1921 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-2019-1921 and fix it if it is affected.

What it is: CVE-2019-1921 is a medium-severity vulnerability in Cisco Email Security Appliance, published on 6 Jul 2019. 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-2019-1921 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-2019-1921/ (Markdown: https://insights.sbomify.com/CVE-2019-1921/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1921
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1921
- OSV: https://osv.dev/vulnerability/CVE-2019-1921

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-1921/
Summaries are generated and may contain mistakes; the official description above is the record.