CVE intelligence and bounded remediation

CVE-2021-34793 — Cisco Adaptive Security Appliance security vulnerability

High CVSS 8.6

A vulnerability in the TCP Normalizer of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software operating in transparent mode could allow an unauthenticated, remote attacker to poison MAC address tables, resulting in a denial of service (DoS) vulnerability. This vulnerability is due to incorrect handling of certain TCP segments when the affected device is operating in transparent mode. An attacker could exploit this vulnerability by sending a crafted TCP segment through an affected device. A successful exploit could allow the attacker to poison the MAC address tables in adjacent devices, resulting in network disruption.

Severity
High
CVSS
8.6 (3.1)
Published
2021-10-27
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-924

Affected products

  • cisco / adaptive_security_appliance
  • cisco / firepower_threat_defense
  • cisco / adaptive_security_appliance_software
  • cisco / asa_5512-x_firmware / 009.008(004.025)
  • cisco / asa_5505_firmware / 009.008(004.025)
  • cisco / asa_5515-x_firmware / 009.008(004.025)

Showing 6 representative product identities from 16 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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