CVE-2020-3259
CVE-2020-3259 is a security flaw in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD), Cisco’s firewall. Attackers can read information from Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) that should be private 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 15 Feb 2024, and says ransomware gangs have used it.[1]
Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) 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. Fixed in version 6.2.3.16, 6.3.0.6, 6.4.0.9 and 6.5.0.5 and others.
Description
CISA calls it an ASA and FTD information disclosure in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD). In its words: “Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an information disclosure vulnerability. An attacker could retrieve memory contents on an affected device, which could lead to the disclosure of confidential information due to a buffer tracking issue when the software parses invalid URLs that are requested from the web services interface. This vulnerability affects only specific AnyConnect and WebVPN configurations.”[1]
The CVE record adds: “A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to retrieve memory contents on an affected device, which could lead to the disclosure of confidential information. The vulnerability is due to a buffer tracking issue when the software parses invalid URLs that are requested from the web services interface. An attacker could exploit this vulnerability by sending a crafted GET request to the web services interface. A successful exploit could allow the attacker to retrieve memory contents, which could lead to the disclosure of confidential information. Note: This vulnerability affects only specific AnyConnect and WebVPN configurations. For more information, see the Vulnerable Products section.”[2]
The underlying weakness is information exposure (CWE-200), in MITRE’s list of common software weaknesses.
It scores 7.5 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 lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| firepower_threat_defense | 6.2.3.16 |
| firepower_threat_defense | 6.3.0.6 |
| firepower_threat_defense | 6.4.0.9 |
| firepower_threat_defense | 6.5.0.5 |
| adaptive_security_appliance_software | 9.8.4.20 |
| adaptive_security_appliance_software | 9.9.2..67 |
| adaptive_security_appliance_software | 9.10.1.40 |
| adaptive_security_appliance_software | 9.12.3.9 |
Most families won’t have Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD); it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 15 Feb 2024, 1,380 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 7 Mar 2024 to fix it.[1] CISA says ransomware gangs have used it.
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 72%. 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: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) 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 (fixed in version 6.2.3.16, 6.3.0.6, 6.4.0.9 and 6.5.0.5 and others), or not in use. CISA gave US government agencies until 7 Mar 2024 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 7.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[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 72%.[4] |
See also
Other Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) flaws
- CVE-2024-20481: ASA and FTD denial-of-service ·
- CVE-2024-20359: ASA and FTD privilege escalation ·
- CVE-2024-20353: ASA and FTD denial of service ·
- CVE-2020-3580: ASA and FTD cross-site scripting (XSS) ·
- CVE-2020-3452: ASA and FTD read-only path traversal ·
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 information exposure flaws
- CVE-2025-68686, Fortinet FortiOS: exposure of sensitive information to an unauthorized actor ·
- CVE-2025-31125, Vitejs: improper access control ·
- CVE-2026-20805, Microsoft Windows: information disclosure ·
- CVE-2021-41277, Metabase: geoJSON API local file inclusion ·
- CVE-2024-24919, Check Point Quantum Security Gateways: information disclosure ·
Added the same day
- CVE-2024-21410, Microsoft Exchange Server: privilege escalation ·
Every Cisco flaw on CISA’s list · Everything added in February 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “Cisco ASA and FTD Information Disclosure Vulnerability”. Known Exploited Vulnerabilities Catalog, added 15 Feb 2024.
- ^ National Institute of Standards and Technology. “CVE-2020-3259 Detail”. National Vulnerability Database, published 6 May 2020.
- ^ Cisco. Advisories and fixes: tools.cisco.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.715, percentile 99.4, 31 Oct 2026.
- CVE Program. “CVE-2020-3259”. 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.