# CVE-2019-1955: Cisco Email Security Appliance Header Injection Vulnerability

> An unauthenticated remote attacker can bypass configured header filters on Cisco Email Security Appliances by sending customized SPF packets, allowing malicious content 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:** 8 Aug 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-x58p-f2fr-mr4f

## What is CVE-2019-1955?

CVE-2019-1955 is a medium-severity vulnerability in Cisco Email Security Appliance (ESA), published on 8 Aug 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliances (ESA) could allow an unauthenticated, remote attacker to bypass configured user filters on the device. The vulnerability is due to incomplete input and validation checking mechanisms for certain 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. A successful exploit could allow the attacker to bypass the header filters that are configured for the affected device, which could allow malicious content to pass through the device.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-1955?

It affects 1 product.


Products: Cisco Email Security Appliance Firmware.

## How do I fix CVE-2019-1955?

No fix has been published for CVE-2019-1955 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1955 being exploited?

There is no known exploitation of CVE-2019-1955 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Email Security Appliance (ESA)

- [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-2019-1955 and fix it if it is affected.

What it is: CVE-2019-1955 is a medium-severity vulnerability in Cisco Email Security Appliance (ESA), published on 8 Aug 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-2019-1955 in the wild and no public exploit code.

Affected product: Cisco Email Security Appliance (ESA). 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-2019-1955/ (Markdown: https://insights.sbomify.com/CVE-2019-1955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1955
- OSV: https://osv.dev/vulnerability/CVE-2019-1955

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-1955/
Summaries are generated and may contain mistakes; the official description above is the record.