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CVE-2025-20333: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

85
Patch now
CRITICAL 9.9EXPLOITEDUPGRADEUPGRADE

CVE-2025-20333 is a critical-severity flaw (CVSS 9.9) 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 VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted H

Why this priority

  • Critical severity
  • EPSS top 1%: very likely to be exploited
  • Exploited in the wild (CISA KEV)

A fixed release or distro patch exists.

Risk facts

CVSS score9.9 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededLow
User interactionNone
EPSS exploit chance71.2% (top 1%)
CISA exploited listYes, fix due 2025-09-26
WeaknessCWE-120
Published2025-09-25
Last modified2026-10-18
Publisher (CNA): Cisco Systems, Inc. · Vendor: cisco

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Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

cisco adaptive security appliance software UPGRADE
Affected: >= 9.12 and < 9.12.4.72 · >= 9.14 and < 9.14.4.28 · >= 9.16 and < 9.16.4.85 · >= 9.17.0 and < 9.17.1.45 · >= 9.18 and < 9.18.4.47 · >= 9.19 and < 9.19.1.37 · >= 9.20 and < 9.20.3.7 · >= 9.22 and < 9.22.1.3
Fixed in: 9.12.4.72, 9.14.4.28, 9.16.4.85, 9.17.1.45, 9.18.4.47, 9.19.1.37, 9.20.3.7, 9.22.1.3
Safe to downgrade to: a release before 9.12
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 UPGRADE
Affected: >= 7.0.0 and < 7.0.8.1 · >= 7.1.0 and < 7.2.9 · >= 7.3.0 and < 7.4.2.4 · 7.6.0
Fixed in: 7.0.8.1, 7.2.9, 7.4.2.4
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. UPGRADE to 7.0.8.1 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade secure-firewall-threat-defense
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade secure-firewall-threat-defense
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, 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
3. If no update is available yet, 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

Fedora 46 · wordpress · FIXED · 7.1.4-1.fc46 · FEDORA-2026-907394725e · source
sudo dnf upgrade --advisory=FEDORA-2026-907394725e
Fedora ELN · rhc · FIXED · 0.3.15-1.eln159 · FEDORA-2026-1cd9f35750 · source
sudo dnf upgrade --advisory=FEDORA-2026-1cd9f35750

Public exploits and detection

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

Advisories and coverage

Official advisories

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-2025-20333?

adaptive security appliance software: upgrade to 9.12.4.72, 9.14.4.28, 9.16.4.85, 9.17.1.45, 9.18.4.47, 9.19.1.37, 9.20.3.7, 9.22.1.3; secure firewall threat defense: upgrade to 7.0.8.1, 7.2.9, 7.4.2.4. Exact commands for each OS are on this page.

Is CVE-2025-20333 being exploited?

Yes. CVE-2025-20333 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2025-20333 affect?

CVE-2025-20333 affects adaptive security appliance software, secure firewall threat defense. Severity is critical (CVSS 9.9). A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an

How urgent is CVE-2025-20333?

Priority 85/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV)

Software pages

Cisco ASA vulnerabilities · Cisco vulnerabilities

Related CVEs

References

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