Cisco · Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense
A missing-authorization flaw in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software lets restricted, remote-access VPN URL endpoints be reached without authentication. An unauthenticated remote attacker can exploit it over the network by sending crafted HTTP(S) requests to the device's web server, with no user interaction or prior configuration needed, to reach endpoints that should require authentication.
Update: On November 5, 2025, Cisco became aware of a new attack variant against devices running Cisco Secure ASA Software or Cisco Secure FTD Software releases that are affected by CVE-2025-20333 and CVE-2025-20362. This attack can cause unpatched devices to unexpectedly reload, leading to denial of service (DoS) conditions. Cisco strongly recommends that all customers upgrade to the fixed software releases that are listed in the Fixed Software ["#fs"] section of this advisory. A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to access restricted URL endpoints that are related to remote access VPN that should otherwise be inaccessible without authentication. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web server on a device. A successful exploit could allow the attacker to access a restricted URL without authentication.
First seen exploited the day it was disclosed. Public exploit code (PoC-in-GitHub) appeared 8 months after disclosure.
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
Unauthenticated HTTP requests to exposed VPN web server
An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web server
Causes device reload, denial of service
This attack can cause unpatched devices to unexpectedly reload, leading to denial of service (DoS) conditions
These detect the technique in general, not this specific vulnerability.
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
Reports are matched by finding the exact id CVE-2025-20362 in their text; nobody has reviewed the match. One passage is shown per report, at most 320 characters, linked to the original.
*Update 2025-09-25: Cisco is aware of new activity targeting certain Cisco Adaptive Security Appliances (ASA) 5500-X Series and has released three CVE’s related to the event: CVE-2025-20333, CVE-2025-20362 and CVE-2025-20363.
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UAT-4356 exploited n-day vulnerabilities (CVE-2025-20333 and CVE-2025-20362) to gain unauthorized access to vulnerable devices.
UAT-4356 exploited n-day vulnerabilities (CVE-2025-20333 and CVE-2025-20362) to gain unauthorized access to vulnerable devices.
UAT-4356 exploited n-day vulnerabilities (CVE-2025-20333 and CVE-2025-20362) to gain unauthorized access to vulnerable devices.
The evidence collected strongly indicates that CVE-2025-20333 and CVE-2025-20362 were used by the attacker in the current attack campaign.
3 passages name itOriginal (opens in a new tab) ↗
Pulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.