VulnerabilityPublished 7 Jan 2026Updated 12 Feb 2026

CVE-2026-20026: Cisco Secure Firewall Threat Defense (FTD) Software · Double Free

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

Not known to be exploited · CVSS 5.8 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.8Medium

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 51% 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 7 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 – 7.7.10.1 57 affected builds	Fixed in–
CiscoCisco UTD SNORT IPS Engine Software	Affected 3.17.0S – 17.18.2 88 affected builds	Fixed in–

AI-suggested

1. Apply Cisco’s security patches for the affected FTD versions as soon as they become available to remediate the buffer handling flaw in Snort 3. 2. Implement network-level filtering to restrict DCE/RPC traffic (typically TCP ports 135, 139, 445) from untrusted or external sources, minimizing exposure to malicious crafted requests. 3. Use segmentation and firewall rules to isolate management and inspection interfaces from general network traffic. 4. Monitor firewall logs and Snort 3 engine status for unusual restarts or performance degradation that may indicate exploitation attempts. 5. Employ intrusion prevention system (IPS) signatures or anomaly detection rules to identify abnormal volumes or patterns of DCE/RPC requests. 6. Conduct regular vulnerability assessments and penetration tests focusing on firewall and network security infrastructure. 7. Maintain up-to-date asset inventories to quickly identify affected Cisco FTD deployments and prioritize patching. 8. Coordinate with Cisco support and subscribe to security advisories for timely updates and mitigation guidance.

Description

Multiple Cisco products are affected by a vulnerability in the processing of DCE/RPC requests that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to leak sensitive information or to restart, resulting in an interruption of packet inspection. This vulnerability is due to an error in buffer handling logic when processing DCE/RPC requests, which can result in a buffer use-after-free read. An attacker could exploit this vulnerability by sending a large number of DCE/RPC requests through an established connection that is inspected by Snort 3. A successful exploit could allow the attacker to unexpectedly restart the Snort 3 Detection Engine, which could cause a denial of service (DoS).

Impact

For European organizations, this vulnerability poses a risk primarily to the availability of network security monitoring and intrusion detection capabilities. Cisco Secure Firewall Threat Defense is widely deployed across enterprises, government agencies, and service providers in Europe to protect critical infrastructure and sensitive data. An attacker exploiting this vulnerability could cause repeated restarts of the Snort 3 Detection Engine, leading to intermittent or sustained denial of service conditions. This interruption reduces visibility into malicious network activity, increasing the risk of undetected attacks or data breaches. Organizations relying heavily on Cisco FTD for perimeter defense or internal segmentation may experience degraded security posture and compliance challenges. Critical sectors such as finance, energy, telecommunications, and public administration in Europe could face operational disruptions if their firewall defenses are impaired. Although the vulnerability does not allow direct data compromise, the loss of detection capability can indirectly facilitate further attacks. The absence of known exploits currently reduces immediate risk, but the broad affected version range and network exposure warrant prompt mitigation.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-dcerpc-vulns-J9HNF4tH (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Feb 2026, 06:44 UTC

Technical details

References

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