VulnerabilityPublished 4 Mar 2026

CVE-2026-20005: Cisco Secure Firewall Threat Defense (FTD) Software · Missing Report of Error Condition

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, 11:52 UTC

CVSS 3.1 base score

5.8Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 44% 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 30 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 7.6.0 – 7.7.10.1 7 affected builds	Fixed in–
CiscoCisco Cyber Vision	Affected 3.0.0 – 5.3.2 52 affected builds	Fixed in–
CiscoCisco UTD SNORT IPS Engine Software	Affected 17.2.1r – 17.18.2 62 affected builds	Fixed in–

AI-suggested

To mitigate CVE-2026-20005, organizations should first verify their Cisco Cyber Vision version and upgrade to the latest patched release once Cisco provides an official fix addressing this vulnerability. In the interim, network administrators can implement traffic filtering to block or limit SSL handshake packets from untrusted or external sources, reducing the attack surface. Deploying intrusion prevention system (IPS) rules to detect and drop malformed SSL handshake packets targeting Snort 3 may also help mitigate exploitation attempts. Monitoring system logs and Snort 3 engine uptime for unexpected restarts can provide early detection of exploitation attempts. Additionally, segmenting the network to isolate Cisco Cyber Vision components from untrusted networks and restricting access to management interfaces can reduce exposure. Regularly reviewing Cisco advisories and subscribing to threat intelligence feeds will ensure timely awareness of patches and exploit developments. Finally, organizations should conduct incident response drills to prepare for potential DoS scenarios impacting their network monitoring capabilities.

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 incomplete parsing of the SSL handshake ingress packets. An attacker could exploit this vulnerability by sending crafted SSL handshake packets. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine restarts unexpectedly.

Impact

The primary impact of CVE-2026-20005 is a denial of service condition against the Snort 3 Detection Engine component within Cisco Cyber Vision. This disruption halts packet inspection, which can blind security monitoring systems to ongoing malicious activities or network anomalies. Organizations using Cisco Cyber Vision for industrial control system (ICS) visibility and threat detection may experience reduced situational awareness, increasing the risk of undetected attacks or operational disruptions. The vulnerability could be exploited by attackers to create windows of opportunity for further intrusion or lateral movement by temporarily disabling network inspection. Given the broad range of affected versions, many organizations worldwide could be impacted, especially those in critical infrastructure sectors such as manufacturing, energy, utilities, and transportation that rely on Cisco Cyber Vision for operational technology (OT) network security. Although the vulnerability does not allow data exfiltration or direct compromise of system integrity, the loss of availability in security monitoring can have cascading effects on incident response and overall network defense posture.

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 4 Mar 2026, 17:34 UTC

Technical details

References

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