CVE-2021-40114: Multiple Cisco products are affected by a vulnerability in the way the Snort detection engine processes ICMP t

This month

MEDIUM 6.8REMOTEDOWNGRADEUPGRADEUPGRADE

CVE-2021-40114 is a medium-severity flaw (CVSS 6.8) affecting secure firewall management center, secure firewall threat defense, unified threat defense. 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 way the Snort detection engine processes ICMP traffic that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper memory resource management while the Snort detection engine is processing ICMP packets. An attacker could exploit this vulnerability by sending a series of ICMP packets throug

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.8 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	2.5% (top 16%)
CISA exploited list	No
Weakness	CWE-770, CWE-401
Published	2021-10-27
Last modified	2026-08-11

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

Last updated 2026-08-11 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-27 19:15 UTCPublished CVE record published
2026-08-11 19:37 UTCUpdated Record last modified

cisco secure firewall management center DOWNGRADE

Affected: 2.9.14.0 · 2.9.15 · 2.9.16 · 2.9.17

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.9.14.0

1. Check installed version

apt-cache policy secure-firewall-management-center || rpm -q secure-firewall-management-center || secure-firewall-management-center --version

2. No fixed release: DOWNGRADE to a release before 2.9.14.0 (Debian / Ubuntu)

apt-cache madison secure-firewall-management-center sudo apt install secure-firewall-management-center=<VERSION_BEFORE_2.9.14.0> sudo apt-mark hold secure-firewall-management-center

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

dnf --showduplicates list secure-firewall-management-center sudo dnf downgrade secure-firewall-management-center-<VERSION_BEFORE_2.9.14.0> sudo dnf versionlock add secure-firewall-management-center

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 UPGRADE

Affected: < 6.4.0.12 · >= 6.5.0 and < 6.6.3 · >= 6.7.0 and < 6.7.0.2

Fixed in: 6.4.0.12, 6.6.3, 6.7.0.2

Safe to downgrade to: a release before 6.5.0

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 6.4.0.12 (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 6.5.0 (Debian / Ubuntu)

apt-cache madison secure-firewall-threat-defense sudo apt install secure-firewall-threat-defense=<VERSION_BEFORE_6.5.0> 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_6.5.0> 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 UPGRADE

Affected: >= 16.12 and < 16.12.6 · >= 17.3 and < 17.3.4a · >= 17.4 and < 17.4.2

Fixed in: 16.12.6, 17.3.4a, 17.4.2

Safe to downgrade to: a release before 16.12

1. Check installed version

apt-cache policy unified-threat-defense || rpm -q unified-threat-defense || unified-threat-defense --version

2. UPGRADE to 16.12.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade unified-threat-defense

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade unified-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 16.12 (Debian / Ubuntu)

apt-cache madison unified-threat-defense sudo apt install unified-threat-defense=<VERSION_BEFORE_16.12> sudo apt-mark hold unified-threat-defense

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

dnf --showduplicates list unified-threat-defense sudo dnf downgrade unified-threat-defense-<VERSION_BEFORE_16.12> sudo dnf versionlock add unified-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.

snort snort UPGRADE

Affected: >= 2.0.0 and < 2.9.18

Fixed in: 2.9.18

Safe to downgrade to: a release before 2.0.0

1. Check installed version

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

2. UPGRADE to 2.9.18 (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 2.0.0 (Debian / Ubuntu)

apt-cache madison snort sudo apt install snort=<VERSION_BEFORE_2.0.0> 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_2.0.0> 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.

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-2021-40114?

secure firewall management center: downgrade or apply the listed mitigation; secure firewall threat defense: upgrade to 6.4.0.12, 6.6.3, 6.7.0.2; unified threat defense: upgrade to 16.12.6, 17.3.4a, 17.4.2. Exact commands for each OS are on this page.

Is CVE-2021-40114 being exploited?

CVE-2021-40114 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-2021-40114 affect?

CVE-2021-40114 affects secure firewall management center, secure firewall threat defense, unified threat defense. Severity is medium (CVSS 6.8). Multiple Cisco products are affected by a vulnerability in the way the Snort detection engine processes ICMP traffic that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. Th

How urgent is CVE-2021-40114?

Priority 50/100. Remotely exploitable, no login, no user action

Software pages

Cisco vulnerabilities · Suricata and Snort vulnerabilities

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References

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