# CVE-2026-20250: Cisco Secure Firewall ASA and FTD DTLS denial of service

Source: https://junglewise.ai/threats/cve-2026-20250-cisco-secure-firewall-asa-and-ftd-dtls-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-20250 · Severity: high · CVSS 8.6 · Published 2026-09-16

Cisco's Secure Firewall appliances (ASA and FTD software) contain a flaw in DTLS message handling that allows remote attackers to crash the firewall without authentication. An attacker can send specially crafted DTLS traffic to force the device to reload, disrupting all traffic protection and network operations until the firewall recovers. This affects organizations relying on these devices to protect corporate networks.

Technologies: [Cisco Secure Firewall ASA Software](https://junglewise.ai/threats/technologies/secure-firewall-asa-software), [Cisco Secure Firewall Threat Defense Software](https://junglewise.ai/threats/technologies/firepower-threat-defense-software). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20250 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20250 being exploited in the wild.

**How severe is CVE-2026-20250?** High severity, with a CVSS score of 8.6, published 16 September 2026.

**Which products and versions are affected?** Cisco Secure Firewall ASA Software 9.22.3.191, 9.23.1.195, 9.24.1.155 (and other vulnerable versions prior to fixed releases 9.22.3.26, 9.23.1.211, 9.24.1.26); Cisco Secure Firewall Threat Defense Software Multiple versions on Secure Firewall 3100 and 4200 Series devices (see Cisco advisory for specific version details).

**Is there a fix for CVE-2026-20250?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20250 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20250?** Check whether you run Cisco Secure Firewall ASA Software or Cisco Secure Firewall Threat Defense Software 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

The vulnerability is a resource management flaw (CWE-772) in DTLS message processing on Cisco Secure Firewall 3100 and 4200 Series devices when DTLS flow offload is enabled (default). An unauthenticated remote attacker can send a crafted stream of DTLS traffic to trigger improper resource handling, causing the affected device to reload. This is a network-reachable denial-of-service attack requiring no authentication or user interaction. Cisco has released software updates and identified a workaround (disabling DTLS flow offload via CLI) that trades DoS protection for reduced throughput and increased CPU utilization.

## Affected products

- Cisco Secure Firewall ASA Software 9.22.3.191, 9.23.1.195, 9.24.1.155 (and other vulnerable versions prior to fixed releases 9.22.3.26, 9.23.1.211, 9.24.1.26)
- Cisco Secure Firewall Threat Defense Software Multiple versions on Secure Firewall 3100 and 4200 Series devices (see Cisco advisory for specific version details)

## Timeline

- 2026-09-16: disclosed: Cisco Security Advisory published
- 2026-09-18: advisory: Advisory updated (version 1.1)

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dtls-dos-Kp57HkyO](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dtls-dos-Kp57HkyO)

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- [Cisco Secure Firewall ASA and FTD SSL VPN denial of service](https://junglewise.ai/threats/cve-2026-76418-a-vulnerability-in-the-remote-access-ssl-vpn-service-of-cisco)
- [Cisco Snort 3 GRE detection engine denial of service](https://junglewise.ai/threats/cve-2026-20179-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Secure Firewall ASA calculation error in security-critical context](https://junglewise.ai/threats/cve-2026-20335-cisco-secure-firewall-asa-calculation-error-in-security-critical)
- [Cisco Secure Firewall improper adherence to coding standards](https://junglewise.ai/threats/cve-2026-20334-cisco-secure-firewall-improper-adherence-to-coding-standards)
- [Cisco Secure Firewall ASA/FTD/FMC incorrect comparison in security context](https://junglewise.ai/threats/cve-2026-20333-cisco-secure-firewall-asa-ftd-fmc-incorrect-comparison-in)