CVE intelligence and bounded remediation

CVE-2026-20021 — Cisco Adaptive Security Appliance Software security vulnerability

Medium CVSS 4.3

A vulnerability in the OSPF protocol of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, adjacent attacker to exhaust memory on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improperly validating input by the OSPF protocol when parsing packets. An attacker could exploit this vulnerability by by sending crafted OSPF packets to an affected device. A successful exploit could allow the attacker to exhaust memory on the affected device, resulting in a DoS condition.

Severity
Medium
CVSS
4.3 (3.1)
Published
2026-03-04
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-401

Affected products

  • cisco / adaptive_security_appliance_software
  • cisco / firepower_threat_defense_software / 6.4.0
  • cisco / firepower_threat_defense_software / 6.4.0.1
  • cisco / firepower_threat_defense_software / 6.4.0.2
  • cisco / firepower_threat_defense_software / 6.4.0.3

Showing 5 representative product identities from 84 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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