Remote Denial of Service Vulnerability in Cisco Secure Firewall Products
CVE-2025-20127

7.7HIGH

Key Information:

Vendor

Cisco
Status
Cisco Adaptive Security Appliance (asa) Software
Cisco Firepower Threat Defense Software
Vendor
CVE Published:
14 August 2025

Badges

👾 Exploit Exists

What is CVE-2025-20127?

A resource exhaustion vulnerability exists in the TLS 1.3 implementation within Cisco Secure Firewall ASA and FTD Software, which affects Cisco Firepower 3100 and 4200 Series devices. An authenticated remote attacker can exploit this vulnerability by initiating a barrage of TLS 1.3 connections using the TLS_CHACHA20_POLY1305_SHA256 cipher. This overloads the system, resulting in a denial of service where no new SSL/TLS or VPN requests are accepted. To restore normal operation, a device reboot is required.

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Affected Version(s)

Cisco Adaptive Security Appliance (ASA) Software 9.20.1

Cisco Adaptive Security Appliance (ASA) Software 9.20.1.5

Cisco Adaptive Security Appliance (ASA) Software 9.20.2

References

https://sec.cloudapps.cisco.com/security/center/content/C...

CVSS V3.1

Score:
7.7
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Changed

Timeline

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

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