CVE-2026-20039
Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL VPN Authentication Denial of Service Vulnerability
- Published
- Updated
- Reserved
- Assigned by
- cisco
Description
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 cause a denial of service (DoS) condition on an affected device. This vulnerability is due to ineffective memory management of the VPN web server. An attacker could exploit this vulnerability by sending a large number of crafted HTTP requests to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
Timeline
ID reserved
By cisco
- 5 months later
· 5 months later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| ciscoCNA (assigner) | 3.1 | High8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.41% · top 64% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.6.
Weakness
Affected products
Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- affected 9.12.3
- affected 9.12.1
- affected 9.12.2
- affected 9.12.4
- affected 9.12.3.2
- affected 9.12.3.7
- affected 9.12.2.5
- affected 9.12.3.12
- affected 9.12.1.3
- affected 9.12.2.4
- affected 9.12.1.2
- affected 9.12.2.9
- affected 9.12.3.9
- affected 9.12.2.1
- affected 9.12.4.2
- affected 9.12.4.4
- affected 9.12.4.7
- affected 9.12.4.8
- affected 9.12.4.10
- affected 9.12.4.13
- affected 9.12.4.18
- affected 9.12.4.24
- affected 9.16.1
- affected 9.12.4.26
- affected 9.16.1.28
- affected 9.12.4.29
- affected 9.16.2
- affected 9.12.4.30
- affected 9.16.2.3
- affected 9.12.4.35
- affected 9.16.2.7
- affected 9.12.4.37
- affected 9.17.1
- affected 9.16.2.11
- affected 9.16.2.13
- affected 9.12.4.39
- affected 9.12.4.38
- affected 9.16.2.14
- affected 9.17.1.7
- affected 9.12.4.40
- and 102 more
Cisco · Cisco Secure Firewall Threat Defense (FTD) Software
- affected 6.4.0.1
- affected 6.4.0.2
- affected 6.4.0.5
- affected 6.4.0
- affected 6.4.0.3
- affected 6.4.0.4
- affected 6.4.0.6
- affected 6.4.0.7
- affected 6.4.0.8
- affected 6.4.0.9
- affected 6.4.0.10
- affected 6.4.0.11
- affected 6.4.0.12
- affected 7.0.0
- affected 7.0.0.1
- affected 7.0.1
- affected 7.1.0
- affected 6.4.0.13
- affected 7.0.1.1
- affected 6.4.0.14
- affected 7.1.0.1
- affected 7.0.2
- affected 6.4.0.15
- affected 7.2.0
- affected 7.0.2.1
- affected 7.0.3
- affected 7.1.0.2
- affected 7.2.0.1
- affected 7.0.4
- affected 7.2.1
- affected 7.0.5
- affected 6.4.0.16
- affected 7.3.0
- affected 7.2.2
- affected 7.2.3
- affected 7.3.1
- affected 7.1.0.3
- affected 7.2.4
- affected 7.0.6
- affected 7.2.5
- and 28 more
What to do
Exploitation: The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
References (1)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-20039)Record last updated .