# CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection

> Unauthenticated remote attackers can cause Cisco ASA and FTD devices to reload via crafted HTTP requests to the SSL VPN service, resulting in denial of service.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Yes, since 11 Aug 2026 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Aug 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-8x4j-5v9x-9frv

## What is CVE-2026-20349?

CVE-2026-20349 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 11 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. 

This vulnerability is due to insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

Weakness: CWE-244 (Improper Clearing of Heap Memory Before Release)

## Which versions are affected by CVE-2026-20349?

It affects 2 products.


Products: Cisco Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense.

## How do I fix CVE-2026-20349?

No fix has been published for CVE-2026-20349 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 14 Aug 2026.

## Is CVE-2026-20349 being exploited?

Yes. Attackers have exploited CVE-2026-20349 in the wild since at least 11 Aug 2026.

Public exploit code:

- Panduan Praktikum Edukasi: Deteksi Versi Cisco ASA & FTD (CVE-2026-20349) (github_poc): https://github.com/ekacs/predicted-cve-2026-20349

## Other vulnerabilities in Cisco Adaptive Security Appliance Software

- [CVE-2025-20333](https://insights.sbomify.com/CVE-2025-20333/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow (critical 9.9, exploited in the wild)
- [CVE-2016-6366](https://insights.sbomify.com/CVE-2016-6366/): Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow (high 8.8, exploited in the wild)
- [CVE-2024-20353](https://insights.sbomify.com/CVE-2024-20353/): Cisco ASA and FTD Denial of Service (high 8.6, exploited in the wild)
- [CVE-2016-6367](https://insights.sbomify.com/CVE-2016-6367/): Cisco Adaptive Security Appliance (ASA) CLI Remote Code Execution (high 7.8, exploited in the wild)
- [CVE-2020-3452](https://insights.sbomify.com/CVE-2020-3452/): Cisco ASA and FTD Read-Only Path Traversal (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20349 and fix it if it is affected.

What it is: CVE-2026-20349 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 11 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2026-20349 in the wild since at least 11 Aug 2026.

Affected product: Cisco Adaptive Security Appliance 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-2026-20349/ (Markdown: https://insights.sbomify.com/CVE-2026-20349/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20349
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20349
- OSV: https://osv.dev/vulnerability/CVE-2026-20349

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-20349/
Summaries are generated and may contain mistakes; the official description above is the record.