CVE-2026-20006: A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall

Routine

MEDIUM 5.8REMOTEDOWNGRADE

CVE-2026-20006 is a medium-severity flaw (CVSS 5.8) affecting secure firewall threat defense. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to unexpectedly restart, resulting in a denial of service (DoS) condition. This vulnerability is due to improper implementation of the TLS protocol. An attacker could exploit this vulnerability by sending a crafted TLS p

Why this priority

Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-388
Published	2026-03-04
Last modified	2026-08-20

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

Last updated 2026-08-20 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-04 18:16 UTCPublished CVE record published
2026-08-20 16:45 UTCUpdated Record last modified

cisco secure firewall threat defense DOWNGRADE

Affected: 7.2.0 · 7.2.0.1 · 7.2.1 · 7.2.2 · 7.2.3 · 7.2.4 · 7.2.4.1 · 7.2.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.2.0

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 7.2.0 (Debian / Ubuntu)

apt-cache madison secure-firewall-threat-defense sudo apt install secure-firewall-threat-defense=<VERSION_BEFORE_7.2.0> 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_7.2.0> 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.

Verify at the official source NVD · CVE Program · 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-2026-20006?

secure firewall threat defense: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-20006 being exploited?

CVE-2026-20006 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-20006 affect?

CVE-2026-20006 affects secure firewall threat defense. Severity is medium (CVSS 5.8). A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to unexpected

How urgent is CVE-2026-20006?

Priority 34/100. Remotely exploitable, no login, no user action

Software pages

Cisco vulnerabilities · Suricata and Snort vulnerabilities

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References

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