Critical Cisco flaw gives hackers three years of network access - AI News Today Recency

# Critical Cisco Flaw Gives Hackers Three Years of Network Access

A maximum-severity vulnerability in Cisco's SD-WAN infrastructure has been actively exploited by threat actors since 2023, allowing attackers to bypass authentication and gain administrative control over critical network systems. The flaw, disclosed on February 25, 2026, represents a significant threat to organizations worldwide, particularly those managing edge network devices in critical infrastructure sectors.[1][2]

Understanding CVE-2026-20127: The Authentication Bypass Threat

The vulnerability, tracked as CVE-2026-20127 with a CVSS score of 10.0, affects Cisco Catalyst SD-WAN Controller (formerly vSmart) and Cisco Catalyst SD-WAN Manager (formerly vManage).[1] An unauthenticated remote attacker can exploit the flaw by sending a crafted request to an affected system, completely bypassing the authentication mechanism without requiring any credentials.[2]

The root cause lies in improper implementation of the peering authentication mechanism, which is designed to verify legitimate network devices attempting to connect to the SD-WAN fabric.[1] Once successfully exploited, attackers gain elevated privileges as a non-root user account, providing them with sufficient access to manipulate network configurations and establish persistent footholds within an organization's infrastructure.[1]

Real-World Exploitation: A Three-Year Campaign

Australian cybersecurity authorities first identified active exploitation of this vulnerability, revealing that malicious actors designated as UAT-8616 have leveraged CVE-2026-20127 since 2023.[1] The threat actor created rogue peers that appeared as legitimate SD-WAN components, allowing them to conduct trusted actions within both the management and control planes of compromised networks.[1]

According to Cisco Talos research, attackers employed a sophisticated multi-stage exploitation strategy.[2] After gaining initial access through CVE-2026-20127, threat actors downgraded the software version on compromised systems to older vulnerable firmware releases. They then exploited a secondary vulnerability, CVE-2022-20775, to escalate privileges and achieve root-level access.[2]

This exploitation pattern indicates a deliberate targeting of network edge devices by cyber threat actors seeking to establish persistent access to high-value organizations, including those in critical infrastructure sectors.[1]

Urgent Government Response and Patching Mandates

The severity of this threat prompted immediate action from cybersecurity authorities worldwide. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-20127 to its Known Exploited Vulnerabilities (KEV) catalog, mandating that Federal Civilian Executive Branch (FCEB) agencies apply security patches within 24 hours.[1] An emergency directive requires patches to be installed by 5:00 PM ET on February 27, 2026.[2]

The Canadian Centre for Cyber Security also issued critical advisories, confirming active exploitation and recommending immediate upgrades to fixed versions.[3] Organizations operating Cisco Catalyst SD-WAN instances in on-premises deployments, Cisco-managed cloud environments, and FedRAMP-compliant cloud infrastructures are all at risk.[3]

Detection and Forensic Analysis Strategies

Organizations must conduct thorough forensic analysis to identify potential compromises. Cisco recommends examining control connection peering events in Catalyst SD-WAN logs, though all peering events require manual validation to distinguish legitimate activity from malicious intrusions.[2]

Defenders should verify the timestamp of each peering event against known maintenance windows and normal operational hours, confirm that public IP addresses correspond to authorized infrastructure, and validate that peer system IPs match documented device assignments within the SD-WAN topology.[2] The Canadian Centre for Cyber Security emphasizes consolidating and monitoring internet gateways, patching systems promptly, hardening configurations, and isolating web-facing applications as critical defensive measures.[3]

Frequently Asked Questions

What systems are affected by CVE-2026-20127?

The vulnerability affects Cisco Catalyst SD-WAN Controller (formerly vSmart) and Cisco Catalyst SD-WAN Manager (formerly vManage) across multiple deployment types, including on-premises installations, Cisco-managed cloud environments, and FedRAMP-compliant cloud infrastructures.[3]

How long has this vulnerability been exploited?

Threat actors have actively exploited CVE-2026-20127 since 2023, making it a three-year campaign of unauthorized network access before the vulnerability was publicly disclosed on February 25, 2026.[1]

What can attackers do after exploiting this vulnerability?

Successful exploitation grants attackers elevated administrative privileges, allowing them to create rogue peers, manipulate network configurations, access NETCONF systems, and establish persistent long-term access to SD-WAN networks.[1][3]

What is the deadline for applying security patches?

Federal agencies must apply patches by 5:00 PM ET on February 27, 2026, as mandated by CISA's emergency directive.[2] All organizations should prioritize patching immediately regardless of sector.

How can organizations detect if they have been compromised?

Organizations should review control connection peering events in their Catalyst SD-WAN logs and validate each event by checking timestamps against maintenance windows, confirming IP addresses match authorized infrastructure, and verifying peer system IPs against documented device assignments.[2]

What makes this vulnerability particularly dangerous?

The combination of a perfect CVSS 10.0 score, unauthenticated remote exploitability, three years of active exploitation before disclosure, and the ability to establish persistent administrative access makes this one of the most critical threats to network infrastructure.[1][2]