VulnerabilityPublished 25 Mar 2026Updated 26 Mar 2026

CVE-2026-20086: Cisco IOS XE Software · Improper Handling of Missing Values

Affects Cisco IOS XE SoftwareSource 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
CiscoCisco IOS XE Software	Affected 17.14.1 – 17.18.1 10 affected builds	Fixed in–

AI-suggested

Apply Cisco's official patches or software updates for IOS XE versions addressing CVE-2026-20086 as soon as they become available. Monitor Cisco security advisories for release information.
Implement network-level filtering to block malformed or suspicious CAPWAP packets at the perimeter and internal network segments to reduce exposure.
Restrict access to wireless controllers by limiting management interfaces to trusted networks and using access control lists (ACLs) to prevent unauthorized packet injection.
Monitor network traffic for anomalous CAPWAP packets and unusual device reloads to detect potential exploitation attempts early.
Employ segmentation to isolate wireless controllers from untrusted networks, minimizing attack surface.
Regularly review and update wireless controller configurations to follow security best practices, including disabling unused services and protocols.
Conduct penetration testing and vulnerability assessments focused on wireless infrastructure to identify and remediate weaknesses proactively.
Maintain an incident response plan that includes procedures for handling wireless network outages caused by DoS attacks.

Description

A vulnerability in the processing of Control and Provisioning of Wireless Access Points (CAPWAP) packets of Cisco IOS XE Wireless Controller Software for the Catalyst CW9800 Family could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of a malformed CAPWAP packet. An attacker could exploit this vulnerability by sending a malformed CAPWAP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition.

Impact

The primary impact of CVE-2026-20086 is a denial of service condition on Cisco Catalyst CW9800 Wireless Controllers, which are widely deployed in enterprise and service provider networks. A successful attack causes the device to reload unexpectedly, resulting in temporary loss of wireless network connectivity for all clients managed by the controller. This can disrupt business operations, especially in environments relying heavily on wireless access for critical applications such as healthcare, finance, education, and manufacturing. The vulnerability does not compromise confidentiality or data integrity but significantly affects availability. Given the unauthenticated, remote nature of the exploit, attackers can launch DoS attacks from anywhere on the network or potentially from the internet if the device is exposed. This could be leveraged as part of a larger attack campaign to degrade network services or cause operational disruptions. Organizations with large-scale wireless deployments using affected Cisco IOS XE versions face increased risk of service outages and potential reputational damage. The lack of known exploits in the wild currently reduces immediate risk, but the high CVSS score and ease of exploitation warrant urgent attention.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-wlc-dos-hnX5KGOm (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Mar 2026, 16:31 UTC

Technical details

References

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