# CVE-2018-15460: Cisco Email Security Appliance URL Filtering Denial of Service Vulnerability

> Unauthenticated remote attackers can cause a denial of service on Cisco Email Security Appliances by sending emails with many whitelisted URLs.

- **Severity:** High 8.6 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Jan 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-q66v-34fh-vw9m

## What is CVE-2018-15460?

CVE-2018-15460 is a high-severity denial of service vulnerability in Cisco Asyncos, published on 10 Jan 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances (ESA) could allow an unauthenticated, remote attacker to cause the CPU utilization to increase to 100 percent, causing a denial of service (DoS) condition on an affected device. The vulnerability is due to improper filtering of email messages that contain references to whitelisted URLs. An attacker could exploit this vulnerability by sending a malicious email message that contains a large number of whitelisted URLs. A successful exploit could allow the attacker to cause a sustained DoS condition that could force the affected device to stop scanning and forwarding email messages.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2018-15460?

It affects 1 product.


Products: Cisco Asyncos.

## How do I fix CVE-2018-15460?

No fix has been published for CVE-2018-15460 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-15460 being exploited?

There is no known exploitation of CVE-2018-15460 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Asyncos

- [CVE-2025-20393](https://insights.sbomify.com/CVE-2025-20393/): Cisco Multiple Products Improper Input Validation (critical 10.0, exploited in the wild)
- [CVE-2026-76519](https://insights.sbomify.com/CVE-2026-76519/): Cisco Secure Email Gateway Relative Path Traversal (critical 9.8, exploited in the wild)
- [CVE-2026-76461](https://insights.sbomify.com/CVE-2026-76461/): Cisco Secure Email Gateway SQL Injection (critical 9.8, exploited in the wild)
- [CVE-2024-20435](https://insights.sbomify.com/CVE-2024-20435/): Command injection in Cisco Secure Web Appliance (high 8.8)
- [CVE-2019-15956](https://insights.sbomify.com/CVE-2019-15956/): Cisco Web Security Appliance Unauthorized Device Reset Vulnerability (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-15460 and fix it if it is affected.

What it is: CVE-2018-15460 is a high-severity denial of service vulnerability in Cisco Asyncos, published on 10 Jan 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-2018-15460 in the wild and no public exploit code.

Affected product: Cisco Asyncos. 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-2018-15460/ (Markdown: https://insights.sbomify.com/CVE-2018-15460/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-15460
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-15460
- OSV: https://osv.dev/vulnerability/CVE-2018-15460

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From sbomify Insights: https://insights.sbomify.com/CVE-2018-15460/
Summaries are generated and may contain mistakes; the official description above is the record.