CVE-2021-1620

A vulnerability in the Internet Key Exchange Version 2 (IKEv2) support for the AutoReconnect feature of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to exhaust the free IP addresses from the assigned local pool. This vulnerability occurs because the code does not release the allocated IP address under certain failure conditions. An attacker could exploit this vulnerability by trying to connect to the device with a non-AnyConnect client. A successful exploit could allow the attacker to exhaust the IP addresses from the assigned local pool, which prevents users from logging in and leads to a denial of service (DoS) condition.

• CWE-563
• CWE-772

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev2-ebFrwMPrPatch, Vendor Advisory
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev2-ebFrwMPrPatch, Vendor Advisory

Published

Sep 23, 2021

Last Modified

Jun 17, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-1614A vulnerability in the Multiprotocol Label Switching (MPLS) …5.3
• CVE-2021-1615A vulnerability in the packet processing functionality of Ci…8.6
• CVE-2021-1616A vulnerability in the H.323 application level gateway (ALG)…4.7
• CVE-2021-1617Multiple vulnerabilities in the web-based management interfa…6.5
• CVE-2021-1618Multiple vulnerabilities in the web-based management interfa…7.2
• CVE-2021-1619A vulnerability in the authentication, authorization, and ac…9.1
• CVE-2021-1621A vulnerability in the Layer 2 punt code of Cisco IOS XE Sof…7.4
• CVE-2021-1622A vulnerability in the Common Open Policy Service (COPS) of …8.6
• CVE-2021-1623A vulnerability in the Simple Network Management Protocol (S…7.7
• CVE-2021-1624A vulnerability in the Rate Limiting Network Address Transla…8.6
• CVE-2021-1625A vulnerability in the Zone-Based Policy Firewall feature of…5.8
• CVE-2021-1626MuleSoft is aware of a Remote Code Execution vulnerability a…9.8