CVE-2024-20353: Cisco ASA and FTD Denial of Service Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 69.8%
EPSS score, percentile 99.4 of all scored records
- How severe?
- 8.6 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline . Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 9.8.1
- 9.8.1.5
- 9.8.1.7
- 9.8.2
- 9.8.2.8
- 9.8.2.14
and 18 more in the table below
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2
- https://nvd.nist.gov/vuln/detail/CVE-2024-20353
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 9.8.1 |
| Affected | 9.8.1.5 |
| Affected | 9.8.1.7 |
| Affected | 9.8.2 |
| Affected | 9.8.2.8 |
| Affected | 9.8.2.14 |
| Affected | 9.8.2.15 |
| Affected | 9.8.2.17 |
| Affected | 9.8.2.20 |
| Affected | 9.8.2.24 |
| Affected | 9.8.2.26 |
| Affected | 9.8.2.28 |
And 175 more version entries in the CVE record.
| Status | Versions |
|---|---|
| Affected | 6.2.3 |
| Affected | 6.2.3.1 |
| Affected | 6.2.3.2 |
| Affected | 6.2.3.3 |
| Affected | 6.2.3.4 |
| Affected | 6.2.3.5 |
| Affected | 6.2.3.6 |
| Affected | 6.2.3.7 |
| Affected | 6.2.3.8 |
| Affected | 6.2.3.10 |
| Affected | 6.2.3.11 |
| Affected | 6.2.3.9 |
And 68 more version entries in the CVE record.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an infinite loop vulnerability that can lead to remote denial of service condition.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2024-20353 to its Known Exploited Vulnerabilities (KEV) catalog on 24 Apr 2024.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 1 May 2024.
- The CVE record was published on 24 Apr 2024, the same day it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 8.6 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 69.8% (percentile 99.4), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
References
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