If left unpatched, CVE-2026-20118 could lead to major system disruptions or data loss.
Status: Awaiting Analysis
Last updated: 🕘 12 Mar 2026, 21:08 UTC
Originally published on: 🕔 11 Mar 2026, 17:16 UTC
Time between publication and last update: 1 days
CVSS Release: version 3
psirt@cisco.com
Primary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
CVE-2026-20118: 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.
The exploitability of CVE-2026-20118 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
CVE-2026-20118 presents a challenge to exploit due to its high attack complexity, but the absence of privilege requirements still makes it a viable target for skilled attackers. A thorough security review is advised.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-20118, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-20118, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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