CVE intelligence and bounded remediation

CVE-2021-34767 — Cisco Ios Xe security vulnerability

High CVSS 7.4

A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.

Severity
High
CVSS
7.4 (3.1)
Published
2021-09-23
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-670

Affected products

  • cisco / ios_xe
  • cisco / ios_xe / 3.15.1xbs
  • cisco / ios_xe / 3.15.2xbs
  • cisco / ios_xe / 16.7.1
  • cisco / ios_xe / 16.7.1a
  • cisco / ios_xe / 16.7.1b

Showing 6 representative product identities from 93 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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