CVE-2023-20109 in IOS
Summary
by MITRE • 10/25/2023
A vulnerability in the Cisco Group Encrypted Transport VPN (GET VPN) feature of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker who has administrative control of either a group member or a key server to execute arbitrary code on an affected device or cause the device to crash. This vulnerability is due to insufficient validation of attributes in the Group Domain of Interpretation (GDOI) and G-IKEv2 protocols of the GET VPN feature. An attacker could exploit this vulnerability by either compromising an installed key server or modifying the configuration of a group member to point to a key server that is controlled by the attacker. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a denial of service (DoS) condition. For more information, see the Details ["#details"] section of this advisory.
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Analysis
by VulDB Data Team • 10/28/2025
The vulnerability identified as CVE-2023-20109 represents a critical security flaw within Cisco's Group Encrypted Transport VPN implementation, specifically affecting IOS and IOS XE software versions. This weakness resides in the Group Domain of Interpretation and G-IKEv2 protocol handling mechanisms that govern GET VPN operations, creating a pathway for authenticated remote attackers to compromise affected network infrastructure. The vulnerability stems from inadequate input validation processes that fail to properly scrutinize attributes within the GDOI and G-IKEv2 protocols, leaving the system susceptible to malicious exploitation attempts.
The technical exploitation of this vulnerability requires an attacker to possess administrative privileges on either a group member device or a key server within the network infrastructure. This prerequisite significantly reduces the attack surface but does not eliminate the severity of potential impact, as the attacker can leverage this access to either compromise the key server directly or manipulate group member configurations to redirect communications toward an attacker-controlled key server. The insufficient validation mechanism allows maliciously crafted attributes to bypass normal security checks, creating a condition where unauthorized code execution becomes possible.
Operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise and potential denial of service conditions. When successfully exploited, the vulnerability enables attackers to execute arbitrary code with the privileges of the affected system, potentially allowing them to install backdoors, exfiltrate sensitive data, or modify network configurations. The system may also experience unexpected reloads or crashes, creating denial of service scenarios that disrupt legitimate network operations and potentially affecting business continuity. This dual nature of impact makes the vulnerability particularly dangerous in enterprise environments where network availability and data integrity are paramount.
Mitigation strategies should prioritize immediate administrative access review and network segmentation to limit potential attack vectors. Organizations should implement strict access controls and monitoring of key server configurations to prevent unauthorized modifications. The vulnerability aligns with CWE-20, representing a weakness in input validation, and maps to ATT&CK techniques involving privilege escalation and execution through legitimate system tools. Network administrators should apply Cisco's official security patches and updates as soon as they become available, while also implementing network monitoring solutions to detect anomalous GDOI and G-IKEv2 traffic patterns that might indicate exploitation attempts. Regular security audits of VPN configurations and access controls remain essential defensive measures against this class of vulnerability.