CVE intelligence and bounded remediation

CVE-2021-1620 — Cisco Ios security vulnerability

High CVSS 7.7

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.

Severity
High
CVSS
7.7 (3.1)
Published
2021-09-23
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-563, CWE-772

Affected products

  • cisco / ios / 12.2(6)i1
  • cisco / ios / 15.1(3)svr1
  • cisco / ios / 15.1(3)svr2
  • cisco / ios / 15.1(3)svr3
  • cisco / ios / 15.1(3)svs
  • cisco / ios / 15.1(3)svs1

Showing 6 representative product identities from 689 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Resource exhaustion and denial of service

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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