CVE-2025-20362
CVE-2025-20362 is a security flaw in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense, Cisco’s firewall. Attackers can reach parts of Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense that should be locked to them from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 25 Sep 2025.[1]
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Cisco has published a fix or advice.
Description
CISA calls it a secure firewall adaptive security (ASA) appliance and secure firewall threat defense (FTD) missing authorization in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense. In its words: “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.”[1]
The CVE record adds: “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…”[2]
The underlying weakness is missing authorization (CWE-862), in MITRE’s list of common software weaknesses.
It scores 8.6 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Cisco’s advisory has them[3]. CISA names the product as Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense.
Most families won’t have Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 25 Sep 2025, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 26 Sep 2025 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 87%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Cisco has published a fix or advice.[3] CISA’s 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).”[1]
- Check whether you use it.Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 26 Sep 2025 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.6.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 87%.[4] |
See also
Other Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense flaws
- CVE-2025-20333: secure firewall adaptive security appliance (ASA) and secure firewall threat defense (FTD) buffer overflow ·
Other Cisco flaws
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-76519, Cisco Secure Email Gateway: relative path traversal ·
- CVE-2026-76504, Cisco Catalyst SD-WAN Manager: hex encoding ·
- CVE-2026-76460, Cisco Identity Services Engine: incorrect use of privileged APIs ·
- CVE-2026-76461, Cisco Secure Email Gateway: SQL injection ·
Other missing authorization flaws
- CVE-2024-57726, SimpleHelp: missing authorization ·
- CVE-2023-52163, Digiever DS-2105 Pro: missing authorization ·
- CVE-2025-40602, SonicWall SMA1000 appliance: sMA1000 missing authorization ·
- CVE-2025-6205, Dassault Systèmes DELMIA Apriso: missing authorization ·
- CVE-2021-3493, Linux Kernel: privilege escalation ·
Added the same day
- CVE-2025-20333, Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense: secure firewall adaptive security appliance (ASA) and secure firewall threat defense (FTD) buffer overflow ·
Every Cisco flaw on CISA’s list · Everything added in September 2025
References
- ^ Cybersecurity and Infrastructure Security Agency. “Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Missing Authorization Vulnerability”. Known Exploited Vulnerabilities Catalog, added 25 Sep 2025.
- ^ National Institute of Standards and Technology. “CVE-2025-20362 Detail”. National Vulnerability Database, published 25 Sep 2025.
- ^ Cisco. Advisories and fixes: sec.cloudapps.cisco.com, sec.cloudapps.cisco.com, sec.cloudapps.cisco.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.871, percentile 99.7, 31 Oct 2026.
- CVE Program. “CVE-2025-20362”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.