Vulnerability Database

328,409

Total vulnerabilities in the database

CVE-2021-23000

On BIG-IP versions 13.1.3.4-13.1.3.6 and 12.1.5.2, if the tmm.http.rfc.enforcement BigDB key is enabled in a BIG-IP system, or the Bad host header value is checked in the AFM HTTP security profile associated with a virtual server, in rare instances, a specific sequence of malicious requests may cause TMM to restart. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.

  • Published: Mar 31, 2021
  • Updated: Nov 16, 2025
  • CVE: CVE-2021-23000
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 7.5
  • AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2:

  • Severity: Low
  • Score: 4.3
  • AV:N/AC:M/Au:N/C:N/I:N/A:P

No CWE or OWASP classifications available.

Software From Fixed in
f5 / ssl_orchestrator 12.1.5.2 12.1.5.2.x
f5 / big-ip_policy_enforcement_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_local_traffic_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_link_controller 12.1.5.2 12.1.5.2.x
f5 / big-ip_global_traffic_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_fraud_protection_service 12.1.5.2 12.1.5.2.x
f5 / big-ip_domain_name_system 12.1.5.2 12.1.5.2.x
f5 / big-ip_ddos_hybrid_defender 12.1.5.2 12.1.5.2.x
f5 / big-ip_application_security_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_application_acceleration_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_analytics 12.1.5.2 12.1.5.2.x
f5 / big-ip_advanced_web_application_firewall 12.1.5.2 12.1.5.2.x
f5 / big-ip_advanced_firewall_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_access_policy_manager 12.1.5.2 12.1.5.2.x
f5 / big-ip_access_policy_manager 13.1.3.4 13.1.3.6
f5 / big-ip_advanced_firewall_manager 13.1.3.4 13.1.3.6
f5 / big-ip_advanced_web_application_firewall 13.1.3.4 13.1.3.6
f5 / big-ip_analytics 13.1.3.4 13.1.3.6
f5 / big-ip_application_acceleration_manager 13.1.3.4 13.1.3.6
f5 / big-ip_application_security_manager 13.1.3.4 13.1.3.6
f5 / big-ip_ddos_hybrid_defender 13.1.3.4 13.1.3.6
f5 / big-ip_domain_name_system 13.1.3.4 13.1.3.6
f5 / big-ip_fraud_protection_service 13.1.3.4 13.1.3.6
f5 / big-ip_global_traffic_manager 13.1.3.4 13.1.3.6
f5 / big-ip_link_controller 13.1.3.4 13.1.3.6
f5 / big-ip_local_traffic_manager 13.1.3.4 13.1.3.6
f5 / big-ip_policy_enforcement_manager 13.1.3.4 13.1.3.6
f5 / ssl_orchestrator 13.1.3.4 13.1.3.6

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.