CVE-2025-20362: Cisco Secure Firewall Adaptive Security…

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-09-25, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-09-26; treat that as the outer limit, not the target.
EPSS 87.1%, percentile 99.8: FIRST’s model estimates a 87.1% chance of exploitation activity in the next 30 days, higher than 99.8% of all scored CVEs (very high). EPSS is a probability, not a verdict.
Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
Editorial verdict: Patch this week. Cisco ASA/FTD VPN Zero-Days Tied to ArcaneDoor — Still live in October 2026: the actor added a persistence mechanism in April 2026 that survives the September 2025 fixes, so ASA/FTD owners with VPN web services need the latest updates and a physical power cycle, not just last year's patch.

What it is

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.

CISA’s summary

Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Software VPN Web Server contain a missing authorization vulnerability. This vulnerability could be chained with CVE-2025-20333.

Weakness type: CWE-862.

Product: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense · Assigned by: cisco · Published: 2025-09-25

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
Cisco	Cisco Secure Firewall Adaptive Security Appliance (ASA) Software	9.8.1, 9.8.1.5, 9.8.1.7, 9.8.2, 9.8.2.8, 9.8.2.14, 9.8.2.15, 9.8.2.17, 9.8.2.20, 9.8.2.24, 9.8.2.26, 9.8.2.28
Cisco	Cisco Secure Firewall Threat Defense (FTD) Software	6.2.3, 6.2.3.1, 6.2.3.2, 6.2.3.3, 6.2.3.4, 6.2.3.5, 6.2.3.6, 6.2.3.7, 6.2.3.8, 6.2.3.10, 6.2.3.11, 6.2.3.9

Severity scores

Scored by	CVSS	Score	Vector
cisco	3.1	6.5 Medium	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N`

Attack vector: network (remotely reachable)
Attack complexity: low
Privileges required: none (no login)
User interaction: none
Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2025-09-25; federal due date 2025-09-26. Known ransomware use: Unknown.
CISA required action: The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
CISA SSVC assessment: exploitation active, automatable yes, technical impact partial.
FIRST EPSS (model of 2026-10-21): 87.09% probability of exploitation activity in the next 30 days; percentile 99.8.

Timeline

2025-09-25 — Added to CISA’s Known Exploited Vulnerabilities catalog
2025-09-25 — CVE record published by cisco
2025-09-25 — erroneo.us brief: Cisco ASA/FTD VPN Zero-Days Tied to ArcaneDoor
2025-09-26 — CISA remediation deadline for US federal agencies
2026-02-26 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.