CVE-2026-20065: Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an un

Routine

MEDIUM 5.8REMOTEUPGRADEDOWNGRADEMITIGATE

CVE-2026-20065 is a medium-severity flaw (CVSS 5.8) affecting snort, secure firewall threat defense, unified threat defense snort intrusion prevention system engine. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection. This vulnerability is due to an error in the binder module initialization logic of the Snort Detection Engine. An attacker could exploit this vulnerability by sending certain packets through an established

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

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 67%)
CISA exploited list	No
Weakness	CWE-667
Published	2026-03-04
Last modified	2026-08-19

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

Last updated 2026-08-19 · 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
2026-08-19 20:36 UTCUpdated Record last modified

cisco snort UPGRADE

Affected: >= 3.0.0-233 and < 3.6.3.0

Fixed in: 3.6.3.0

Safe to downgrade to: a release before 3.0.0-233

1. Check installed version

apt-cache policy snort || rpm -q snort || snort --version

2. UPGRADE to 3.6.3.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade snort

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade snort

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 3.0.0-233 (Debian / Ubuntu)

apt-cache madison snort sudo apt install snort=<VERSION_BEFORE_3.0.0-233> sudo apt-mark hold snort

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list snort sudo dnf downgrade snort-<VERSION_BEFORE_3.0.0-233> sudo dnf versionlock add snort

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.

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.

cisco unified threat defense snort intrusion prevention system engine MITIGATE

Affected: 17.2.1r · 17.3.1a · 17.3.2 · 17.3.3 · 17.3.4 · 17.3.4a · 17.3.5 · 17.3.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 17.2.1r

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.

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-2026-20065?

snort: upgrade to 3.6.3.0; secure firewall threat defense: downgrade or apply the listed mitigation; unified threat defense snort intrusion prevention system engine: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-20065 being exploited?

CVE-2026-20065 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-2026-20065 affect?

CVE-2026-20065 affects snort, secure firewall threat defense, unified threat defense snort intrusion prevention system engine. Severity is medium (CVSS 5.8). Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection

How urgent is CVE-2026-20065?

Priority 33/100. Remotely exploitable, no login, no user action

Software pages

Cisco vulnerabilities · Suricata and Snort vulnerabilities

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References

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