CVE-2026-20336: Cisco Secure Firewall software resource lifecycle vulnerability

CVE-2026-20336 · Severity: high · CVSS 8.8 · Published 2026-09-16

Cisco's Secure Firewall products (ASA, Threat Defense, and Management Center) contain a flaw involving improper control of system resources throughout their lifetime—such as uninitialized variables or null pointer dereferences. An authenticated attacker with network access could exploit this to cause service disruption or potentially gain unauthorized access to security appliance functionality, undermining the protection these firewalls provide.

Technologies: Cisco Secure Firewall Adaptive Security Appliance, Cisco Secure Firewall Threat Defense, Cisco Secure Firewall Management Center. Vendors: Cisco.

Quick answers

Is CVE-2026-20336 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-20336 being exploited in the wild.
How severe is CVE-2026-20336?
High severity, with a CVSS score of 8.8, published 16 September 2026.
Which products and versions are affected?
Cisco Secure Firewall Adaptive Security Appliance Multiple releases (see vendor advisory for fixed releases); Cisco Secure Firewall Threat Defense Multiple releases (see vendor advisory for fixed releases); Cisco Secure Firewall Management Center Multiple releases (see vendor advisory for fixed releases).
Is there a fix for CVE-2026-20336?
A patch was published on 2026-09-16: Fixed software releases made available by Cisco Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-20336 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-20336?
Check whether you run Cisco Secure Firewall Adaptive Security Appliance, Cisco Secure Firewall Threat Defense or Cisco Secure Firewall Management Center at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

CVE-2026-20336 addresses improper control of a resource through its lifetime (CWE-664), covering uninitialized variables, null pointers, and resource lifecycle issues. This vulnerability affects Cisco Secure Firewall Adaptive Security Appliance (ASA), Secure Firewall Threat Defense (FTD), and Secure Firewall Management Center (FMC) software. The vulnerability requires network access and local privilege context to exploit; it was discovered during internal security review. An attacker can achieve denial of service or information disclosure depending on the specific resource mismanagement instance. Cisco has released fixed software versions, and no workarounds are available.

Affected products

  • Cisco Secure Firewall Adaptive Security Appliance Multiple releases (see vendor advisory for fixed releases)
  • Cisco Secure Firewall Threat Defense Multiple releases (see vendor advisory for fixed releases)
  • Cisco Secure Firewall Management Center Multiple releases (see vendor advisory for fixed releases)

Timeline

  • 2026-09-16: disclosed: Cisco security advisory published
  • 2026-09-16: patched: Fixed software releases made available by Cisco

References

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