VulnerabilityPublished 25 Mar 2026Updated 26 Mar 2026

CVE-2026-20012: Cisco IOS · Memory Leak

Affects Cisco IOSSource CVE Database V5

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Not known to be exploited · CVSS 8.6 High.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

8.6High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% 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:H

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

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: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 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
CiscoIOS	Affected 15.0(2)EA – 15.9(3)M12 553 affected builds	Fixed in–
CiscoCisco Secure Firewall Adaptive Security Appliance (ASA) Software	Affected 9.8.1 – 9.23.1.13 235 affected builds	Fixed in–
CiscoCisco IOS XE Software	Affected 3.5.0E – 17.18.1w 378 affected builds	Fixed in–
CiscoCisco Secure Firewall Threat Defense (FTD) Software	Affected 6.2.3 – 7.7.10.1 105 affected builds	Fixed in–

AI-suggested

Monitor network traffic for anomalous or malformed IKEv2 packets, especially from untrusted sources, to detect potential exploitation attempts.
Implement network-level filtering or rate limiting on UDP port 500 and 4500 (IKEv2 ports) at perimeter firewalls to restrict exposure to untrusted networks.
Segment and isolate VPN and firewall infrastructure to limit attack surface and lateral movement.
Apply Cisco security advisories and patches promptly once released; track Cisco’s official channels for updates on this vulnerability.
Consider temporary mitigation by disabling IKEv2 if feasible and if it does not disrupt critical services, until patches are applied.
Schedule maintenance windows to allow for manual reboots if devices become unstable or unresponsive due to exploitation.
Maintain up-to-date backups and configuration snapshots to enable rapid recovery.
Conduct internal vulnerability scanning and penetration testing focused on IKEv2 implementations to identify exposure.
Educate network operations and security teams about this vulnerability and signs of exploitation to improve detection and response readiness.

Description

A vulnerability in the Internet Key Exchange version 2 (IKEv2) feature of Cisco IOS Software, Cisco IOS XE Software, Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a memory leak, resulting in a denial of service (DoS) condition on an affected device. This vulnerability is due to improper parsing of IKEv2 packets. An attacker could exploit this vulnerability by sending crafted IKEv2 packets to an affected device. A successful exploit of Cisco IOS Software and IOS XE Software could allow the attacker to cause the affected device to reload, resulting in a DoS condition. A successful exploit of Cisco Secure Firewall ASA Software and Secure FTD Software could allow the attacker to partially exhaust system memory, resulting in system instability, such as the inability to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.

Impact

The primary impact of CVE-2026-20012 is denial of service on critical network infrastructure devices. For organizations worldwide using Cisco IOS and IOS XE routers, exploitation can cause unexpected device reloads, leading to network outages and disruption of services dependent on these routers. For Cisco ASA and Secure Firewall Threat Defense deployments, the memory leak can degrade system stability and prevent new VPN sessions, impacting remote access and secure communications. This can affect enterprise networks, service providers, and government agencies that rely on Cisco VPN and firewall solutions for secure connectivity. The inability to establish new VPN sessions can disrupt business continuity, remote workforce access, and inter-site communications. The requirement for manual reboot to recover increases operational overhead and potential downtime. Although confidentiality and integrity are not directly compromised, the availability impact can have cascading effects on organizational operations, incident response, and security posture. The broad range of affected software versions and Cisco’s market dominance in networking equipment means this vulnerability poses a significant risk globally.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-ios-dos-kPEpQGGK (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Mar 2026, 16:32 UTC

Technical details

References

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