# CVE-2025-20135: Cisco Adaptive Security Appliance and Firepower Threat Defense Software DHCP Denial of Service Vulnerability

> An unauthenticated adjacent attacker can cause a denial of service by exhausting memory via crafted DHCPv4 packets on Cisco ASA and FTD devices.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Aug 2025
- **Updated:** 14 Aug 2025
- **Also known as:** GHSA-j8qj-frmg-5g7v

## What is CVE-2025-20135?

CVE-2025-20135 is a medium-severity denial of service vulnerability in Cisco Adaptive Security Appliance (ASA) Software, published on 14 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the DHCP client functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, adjacent attacker to exhaust available memory.

This vulnerability is due to improper validation of incoming DHCP packets. An attacker could exploit this vulnerability by repeatedly sending crafted DHCPv4 packets to an affected device. A successful exploit could allow the attacker to exhaust available memory, which would affect availability of services and prevent new processes from starting, resulting in a Denial of Service (DoS) condition that would require a manual reboot.
Note: On Cisco Secure FTD Software, this vulnerability does not affect management interfaces.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2025-20135?


## How do I fix CVE-2025-20135?

No fix has been published for CVE-2025-20135 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-20135 being exploited?

There is no known exploitation of CVE-2025-20135 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-20135 and fix it if it is affected.

What it is: CVE-2025-20135 is a medium-severity denial of service vulnerability in Cisco Adaptive Security Appliance (ASA) Software, published on 14 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-20135 in the wild and no public exploit code.

Affected product: Cisco Adaptive Security Appliance (ASA) Software. 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-2025-20135/ (Markdown: https://insights.sbomify.com/CVE-2025-20135/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-20135
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-20135
- OSV: https://osv.dev/vulnerability/CVE-2025-20135

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-20135/
Summaries are generated and may contain mistakes; the official description above is the record.