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

Patch now

HIGH 8.6EXPLOITEDREMOTEMITIGATEDOWNGRADE

CVE-2026-20349 is a high-severity flaw (CVSS 8.6) affecting adaptive security appliance software, secure firewall threat defense, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 vu

Why this priority

High severity
Exploited in the wild (CISA KEV)
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.6 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	Yes, fix due 2026-08-14
Weakness	CWE-244
Published	2026-08-11
Last modified	2026-10-26

Publisher (CNA): Cisco Systems, Inc. · Vendor: cisco

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-11Exploited Added to the CISA Known Exploited Vulnerabilities list
2026-08-11 17:17 UTCPublished CVE record published
2026-08-14Deadline CISA due date for US federal agencies to patch
2026-10-26 13:10 UTCUpdated Record last modified

cisco adaptive security appliance software MITIGATE

Affected: 9.16.1 · 9.16.1.28 · 9.16.2 · 9.16.2.3 · 9.16.2.7 · 9.16.2.11 · 9.16.2.13 · 9.16.2.14

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.16.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

cisco secure firewall threat defense DOWNGRADE

Affected: 7.0.0 · 7.0.0.1 · 7.0.1 · 7.0.1.1 · 7.0.2 · 7.0.2.1 · 7.0.3 · 7.0.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0.0

1. Check installed version

apt-cache policy secure-firewall-threat-defense || rpm -q secure-firewall-threat-defense || secure-firewall-threat-defense --version

2. No fixed release: DOWNGRADE to a release before 7.0.0 (Debian / Ubuntu)

apt-cache madison secure-firewall-threat-defense sudo apt install secure-firewall-threat-defense=<VERSION_BEFORE_7.0.0> sudo apt-mark hold secure-firewall-threat-defense

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list secure-firewall-threat-defense sudo dnf downgrade secure-firewall-threat-defense-<VERSION_BEFORE_7.0.0> sudo dnf versionlock add secure-firewall-threat-defense

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · flare-im · FIXED · 0.22.7-1.fc46 · FEDORA-2026-cd5e8062a1 · source

sudo dnf upgrade --advisory=FEDORA-2026-cd5e8062a1

Fedora ELN · libdnf · FIXED · 0.76.0-2.eln159 · FEDORA-2026-dbd263e9d4 · source

sudo dnf upgrade --advisory=FEDORA-2026-dbd263e9d4

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: ekacs/predicted-cve-2026-20349 (1 stars)

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-20349?

adaptive security appliance software: mitigate or apply the listed mitigation; secure firewall threat defense: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-20349 being exploited?

Yes. CVE-2026-20349 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2026-20349 affect?

CVE-2026-20349 affects adaptive security appliance software, secure firewall threat defense. Severity is high (CVSS 8.6). 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 d

How urgent is CVE-2026-20349?

Priority 76/100. High severity; Exploited in the wild (CISA KEV); Remotely exploitable, no login, no user action

Software pages

Cisco ASA vulnerabilities · Cisco vulnerabilities

References

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