Cyber Resilience

CVE-2021-1620

High

Published: 23 September 2021

Published
23 September 2021
Modified
11 September 2025
KEV Added
Patch
CVSS Score v3.1 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
EPSS Score 0.0033 56.3th percentile
Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-1620 is a high-severity Assignment to Variable without Use (CWE-563) vulnerability in Cisco Ios. Its CVSS base score is 7.7 (High).

Operationally, ranked in the top 43.7% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

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…

more

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(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

cisco
ios
12.2\(6\)i1, 15.1\(3\)svr1, 15.1\(3\)svr2, 15.1\(3\)svr3, 15.1\(3\)svs
cisco
ios xe
16.1.1, 16.1.2, 16.1.3, 16.10.1, 16.10.1a

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-772

Ensures network resources are released once the session ends or becomes inactive, closing the window for missing-release weaknesses.

References