VulnerabilityPublished 4 Mar 2026

CVE-2026-20073: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Improper Access Control

Affects Cisco Secure Firewall Adaptive Security Appliance (ASA) 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 34% 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:L/A:N

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

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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within 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 Adaptive Security Appliance (ASA) Software	Affected 9.12.1 – 9.23.1.19 159 affected builds	Fixed in–
CiscoCisco Secure Firewall Threat Defense (FTD) Software	Affected 6.4.0 – 7.7.10.1 75 affected builds	Fixed in–

AI-suggested

Monitor memory usage closely on all Cisco ASA and FTD devices, especially those configured in clusters, to detect and prevent memory exhaustion conditions.
Limit cluster sizes and replication loads to reduce the risk of memory exhaustion during access control rule synchronization.
Apply network segmentation and zero-trust principles to minimize the impact of any unauthorized traffic that bypasses firewall rules.
Implement strict ingress and egress filtering on upstream devices to reduce exposure to potentially malicious traffic targeting this vulnerability.
Regularly audit firewall rule sets and cluster configurations to ensure they follow best practices and minimize complexity.
Stay alert for Cisco security advisories and apply patches or updates as soon as Cisco releases fixes addressing this vulnerability.
Use intrusion detection and prevention systems (IDS/IPS) to monitor for anomalous traffic patterns indicative of access control bypass attempts.
Employ multi-factor authentication and strong access controls on management interfaces to prevent attackers from gaining additional footholds.
Conduct penetration testing and vulnerability assessments focusing on firewall cluster configurations to identify potential exploitation paths.
Maintain comprehensive logging and monitoring to quickly detect and respond to suspicious activity related to firewall bypass attempts.

Description

A vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to send traffic that should be denied through an affected device. This vulnerability is due to improper error handling when an affected device that is joining a cluster runs out of memory while replicating access control rules. An attacker could exploit this vulnerability by sending traffic that should be blocked through the device. A successful exploit could allow the attacker to bypass access controls and reach devices in protected networks.

Impact

The impact of CVE-2026-20073 is primarily on the integrity of network security controls. Successful exploitation allows attackers to bypass firewall access control rules, potentially enabling unauthorized lateral movement within protected networks. This can lead to exposure of sensitive internal systems, data exfiltration, or further compromise of critical infrastructure. Since the vulnerability requires no authentication or user interaction, it can be exploited remotely by attackers scanning for vulnerable devices. Organizations relying on Cisco ASA and FTD firewalls for perimeter defense or segmentation could see significant security posture degradation. The lack of confidentiality and availability impact reduces the risk of direct data leaks or denial of service, but the integrity compromise is serious enough to facilitate advanced persistent threats or ransomware attacks. The widespread use of Cisco ASA devices in enterprises, government, and critical infrastructure sectors worldwide amplifies the potential global impact. Additionally, the vulnerability affects cluster configurations, which are common in high-availability deployments, increasing the attack surface. Without timely mitigation, attackers could exploit this flaw to evade detection and controls, undermining trust in network defenses.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-aclbypass-dos-CVxVRSvQ (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Mar 2026, 18:32 UTC

Technical details

References

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