VulnerabilityPublished 25 Mar 2026Updated 26 Mar 2026

CVE-2026-20084: Cisco IOS XE Software · Uncontrolled Resource Consumption

Affects Cisco IOS XE SoftwareSource CVE Database V5

Compare

Not known to be exploited · CVSS 8.6 High.

Data as of 30 Oct 2026, 06:59 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 29 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 16.6.1 – 17.18.1 107 affected builds	Fixed in–

AI-suggested

To mitigate CVE-2026-20084, organizations should first review and apply any Cisco-recommended workarounds that restrict or filter BOOTP traffic between VLANs to prevent unauthorized forwarding. Network administrators should disable DHCP snooping on interfaces or VLANs where it is not required, minimizing the attack surface. Implementing strict VLAN segmentation and access control lists (ACLs) to block BOOTP packets from untrusted sources can reduce exposure. Monitoring CPU utilization and network traffic patterns on affected switches can help detect anomalous activity indicative of exploitation attempts. Organizations should prioritize upgrading to patched Cisco IOS XE versions once Cisco releases updates addressing this vulnerability. Until patches are available, consider isolating vulnerable switches from untrusted networks or limiting management access to trusted personnel and networks. Regularly auditing network device configurations and applying Cisco security advisories promptly will enhance resilience. Additionally, deploying network intrusion detection systems (NIDS) capable of identifying abnormal BOOTP traffic patterns can provide early warning of exploitation attempts.

Description

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition. This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition. Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets. There are workarounds that address this vulnerability.

Impact

The primary impact of CVE-2026-20084 is a denial of service condition on Cisco Catalyst 9000 Series Switches running vulnerable IOS XE versions. This can cause critical network infrastructure to become unreachable and unable to forward traffic, severely disrupting enterprise and service provider networks. The VLAN leakage caused by forwarding BOOTP packets across VLANs can also lead to unintended information exposure between network segments, potentially violating network segmentation policies. High CPU utilization induced by the exploit can degrade overall device performance, affecting multiple services relying on the switch. Organizations relying on these switches for core or distribution layer networking may experience outages, impacting business operations, customer services, and potentially causing financial and reputational damage. The vulnerability’s exploitation requires no authentication and no user interaction, making it accessible to remote attackers scanning for vulnerable devices. Given the widespread deployment of Cisco Catalyst 9000 switches in large enterprises, data centers, and service providers worldwide, the scope of impact is extensive. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-bootp-WuBhNBxA (opens in a new tab)

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

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

Technical details

References

Community reviews

Related threats