VulnerabilityPublished 11 Mar 2026

CVE-2026-20118: Cisco IOS XR Software · Improper Cleanup on Thrown Exception

Affects Cisco IOS XR SoftwareSource CVE Database V5

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Not known to be exploited · CVSS 6.8 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

6.8Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: High
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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 11 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 XR Software	Affected 7.9.1 – 25.1.2 23 affected builds	Fixed in–

AI-suggested

Organizations should implement the following specific mitigation steps: 1) Identify and inventory all Cisco devices running affected IOS XR versions, focusing on NCS 5500 Series with NC57 line cards and NCS 5700 Routers. 2) Apply Cisco-released patches or software updates addressing this vulnerability as soon as they become available; prioritize upgrades to fixed versions beyond the affected releases listed. 3) Implement network segmentation and access control lists (ACLs) to restrict unsolicited or untrusted traffic to interfaces running vulnerable software, reducing exposure to crafted packet flows. 4) Monitor network traffic for unusual patterns, such as continuous streams of malformed or crafted packets targeting EPNI interfaces, using intrusion detection/prevention systems (IDS/IPS) and network telemetry. 5) Establish alerting for interface errors, packet drops, or NPU/ASIC processing anomalies that may indicate exploitation attempts. 6) Engage Cisco TAC promptly if suspicious activity or exploitation is suspected to receive guidance and support. 7) Review and test network redundancy and failover configurations to ensure resilience against potential DoS conditions caused by this vulnerability. 8) Incorporate this vulnerability into incident response and vulnerability management workflows to ensure timely detection and remediation. These targeted actions go beyond generic advice by focusing on specific device types, traffic patterns, and operational monitoring relevant to this vulnerability.

Description

A vulnerability in the handling of an Egress Packet Network Interface (EPNI) Aligner interrupt in Cisco IOS XR Software for Cisco Network Convergence System (NCS) 5500 Series with NC57 line cards and Cisco NCS 5700 Routers and Cisco IOS XR Software for Third Party Software could allow an unauthenticated, remote attacker to cause the network processing unit (NPU) and ASIC to stop processing, preventing traffic from traversing the interface. This vulnerability is due to the corruption of packets in specific cases when an EPNI Aligner interrupt is triggered while an affected device is experiencing heavy transit traffic. An attacker could exploit this vulnerability by sending a continuous flow of crafted packets to an interface of the affected device. A successful exploit could allow the attacker to cause persistent, heavy packet loss, resulting in a denial of service (DoS) condition. Note: If active exploitation of this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider. Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates. This change was made because the affected device operates within a critical network segment where compromise could lead to significant disruption or exposure, thereby elevating the overall risk beyond the base technical severity.

Impact

The primary impact of CVE-2026-20118 is a denial of service (DoS) condition caused by the halting of packet processing on affected interfaces. For organizations, this can lead to significant network disruption, especially since the affected devices are core routing platforms (Cisco NCS 5500 and 5700 series) deployed in critical network segments such as service provider backbones, large enterprise WANs, and data center interconnects. Persistent packet loss and interface outages can degrade network availability, interrupt business operations, and impact dependent services. The inability to forward traffic can also affect redundancy and failover mechanisms, potentially cascading failures across network infrastructure. Since the vulnerability can be triggered remotely without authentication, attackers can exploit it from outside the network perimeter, increasing the risk of widespread disruption. Although no confidentiality or integrity impacts are noted, the availability impact alone is significant given the critical role of these devices. The elevated Cisco Security Impact Rating reflects the operational importance of these platforms and the potential for severe service degradation or outages if exploited.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xrncs-epni-int-dos-TWMffUsN (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Mar 2026, 17:16 UTC

Technical details

References

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