VulnerabilityPublished 4 Mar 2026

CVE-2026-20065: Cisco Secure Firewall Threat Defense (FTD) Software · Improper Locking

Affects Cisco Secure Firewall Threat Defense (FTD) SoftwareSource CVE Database V5

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Not known to be exploited · CVSS 5.8 Medium.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

5.8Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
CiscoCisco Secure Firewall Threat Defense (FTD) Software	Affected 7.0.0 – 7.6.0 50 affected builds	Fixed in–
CiscoCisco UTD SNORT IPS Engine Software	Affected 17.2.1r – 17.18.2 71 affected builds	Fixed in–

AI-suggested

Monitor Cisco's official security advisories and promptly apply patches or updates once released for affected FTD versions.
If patches are not yet available, consider temporarily disabling Snort 3 Detection Engine or limiting its exposure to untrusted networks to reduce attack surface.
Implement network segmentation and strict access controls to limit the ability of attackers to send crafted packets to the FTD devices.
Employ external intrusion detection systems to monitor for anomalous traffic patterns that may indicate exploitation attempts targeting Snort 3. 5. Regularly audit and review firewall logs for unexpected restarts or failures in the detection engine. 6. Use Cisco's recommended configuration best practices to harden FTD deployments, including restricting management interfaces and enabling logging and alerting for engine restarts. 7. Consider deploying redundant firewall systems or failover mechanisms to maintain inspection capabilities during potential DoS events. 8. Educate network security teams about this vulnerability to ensure rapid detection and response to any suspicious activity related to Snort 3 restarts.

Description

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 connection that is parsed by Snort 3. A successful exploit could allow the attacker to cause a DoS condition when the Snort 3 Detection Engine restarts unexpectedly.

Impact

The primary impact of CVE-2026-20065 is a denial-of-service condition caused by the unexpected restart of the Snort 3 Detection Engine within Cisco FTD devices. This interruption disables packet inspection temporarily, potentially allowing malicious traffic to pass through the firewall undetected. Organizations relying on Cisco FTD for perimeter defense, intrusion detection, and prevention could experience reduced security posture during exploitation. This could lead to increased risk of network breaches, malware infiltration, or data exfiltration during the downtime. Critical infrastructure, government networks, financial institutions, and enterprises with high security requirements are particularly at risk. The vulnerability does not compromise confidentiality or integrity directly but affects availability, which is a key security pillar. The ease of remote exploitation without authentication increases the risk of automated attacks or scanning by threat actors. However, the lack of known exploits in the wild and the medium severity rating suggest the threat is moderate but should not be underestimated given the widespread deployment of Cisco FTD products globally.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-multi-dos-XFWkWSwz (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Mar 2026, 20:17 UTC

Technical details

References

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