VulnerabilityPublished 4 Mar 2026

CVE-2026-20066: Cisco Secure Firewall Threat Defense (FTD) Software · Uncontrolled Resource Consumption

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: 0.4% chance of exploitation in 30 days – higher than 41% 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 7.4.0 – 7.7.10.1 16 affected builds	Fixed in–
CiscoCisco UTD SNORT IPS Engine Software	Affected 17.2.1r – 17.18.2 71 affected builds	Fixed in–

AI-suggested

Apply Cisco’s security updates and patches for all affected versions of Cisco Secure Firewall Threat Defense software as soon as they become available.
If JSTokenizer functionality is not required for your environment, disable it to reduce the attack surface.
Monitor network traffic for unusual HTTP packets that could indicate attempts to exploit this vulnerability, focusing on JavaScript content inspection.
Implement network segmentation and strict access controls to limit exposure of Cisco FTD devices to untrusted networks.
Regularly audit and update firewall and intrusion detection/prevention system configurations to ensure best practices are followed.
Employ layered security controls such as endpoint protection and network anomaly detection to mitigate risks during potential downtime of the Snort engine.
Maintain up-to-date incident response plans to quickly address any denial-of-service events impacting firewall inspection 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 an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. An attacker could exploit this vulnerability by sending crafted HTTP 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. JSTokenizer is not enabled by default.

Impact

The primary impact of this vulnerability is a denial-of-service condition affecting the availability of Cisco Secure Firewall Threat Defense’s packet inspection capabilities. When exploited, the Snort 3 Detection Engine restarts, causing temporary interruption in traffic inspection and potentially allowing malicious or unauthorized traffic to bypass security controls. This can degrade network security posture and increase the risk of further attacks or data exfiltration during the downtime. Organizations relying on Cisco FTD for perimeter defense or internal segmentation may experience reduced effectiveness of their intrusion detection and prevention systems. Although confidentiality and integrity are not directly impacted, the loss of availability can have cascading effects on overall network security and operational continuity. The fact that exploitation requires no authentication and can be performed remotely increases the risk, especially in environments where JSTokenizer is enabled. However, since JSTokenizer is disabled by default, the exposure is somewhat limited. No known exploits in the wild reduce immediate risk but do not eliminate the need for remediation.

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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