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HighKEV

CVE-2024-20353 — Cisco ASA and FTD Denial of Service Vulnerability

CVE-2024-20353 · Secure Firewall ASA · CVSS 8.6 · KEV

In brief

Severity · CVSS
High8.6CVSS 3.1, High
EPSS
71%
CISA KEV
Known exploited, listed since 24 Apr 2024
CERT-FR
No advisory or alert referenced in the catalog
Vendor
Cisco
Published · Modified
·
Last verified

Summary

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.

Weakness: CWE-835

Title, description and the vendor's statements are quoted from the CVE record; a vendor's advisory is summarised in Patcharo's words, with a link.

Affected and fixed versions

Per product and release branch, as the vendor's CVE record and official advisory state them. A fixed release is shown only when a document names it: the vendor's, or CERT-FR's for Check Point, with its source.

18 branches without a precise fixed release

Cisco Adaptive Security Appliance (ASA) Software

Source: CVE-2024-20353cisco-sa-asaftd-websrvs-dos-X8gNucD2

  1. 9.20
    Affected versions9.20.1, 9.20.1.5, 9.20.2
    First fixed releaseNot published in the sources followed
  2. 9.19
    Affected versions9.19.1, 9.19.1.5, 9.19.1.9, 9.19.1.12
    8 releases listed9.19.1, 9.19.1.5, 9.19.1.9, 9.19.1.12, 9.19.1.18, 9.19.1.22, 9.19.1.24, 9.19.1.27
    First fixed releaseNot published in the sources followed
  3. 9.18
    Affected versions9.18.1, 9.18.1.3, 9.18.2, 9.18.2.5
    15 releases listed9.18.1, 9.18.1.3, 9.18.2, 9.18.2.5, 9.18.2.7, 9.18.2.8, 9.18.3, 9.18.3.39, 9.18.3.46, 9.18.3.53, 9.18.3.55, 9.18.3.56, 9.18.4, 9.18.4.5, 9.18.4.8
    First fixed releaseNot published in the sources followed
  4. 9.17End of life
    Affected versions9.17.1, 9.17.1.7, 9.17.1.9, 9.17.1.10
    10 releases listed9.17.1, 9.17.1.7, 9.17.1.9, 9.17.1.10, 9.17.1.11, 9.17.1.13, 9.17.1.15, 9.17.1.20, 9.17.1.30, 9.17.1.33
    First fixed releaseNot published in the sources followed
  5. 9.16
    Affected versions9.16.1, 9.16.1.28, 9.16.2, 9.16.2.3
    25 releases listed9.16.1, 9.16.1.28, 9.16.2, 9.16.2.3, 9.16.2.7, 9.16.2.11, 9.16.2.13, 9.16.2.14, 9.16.3, 9.16.3.3, 9.16.3.14, 9.16.3.15, 9.16.3.19, 9.16.3.23, 9.16.4, 9.16.4.9, 9.16.4.14, 9.16.4.18, 9.16.4.19, 9.16.4.27, 9.16.4.38, 9.16.4.39, 9.16.4.42, 9.16.4.48, 9.16.4.55
    First fixed releaseNot published in the sources followed
  6. 9.15End of life
    Affected versions9.15.1, 9.15.1.1, 9.15.1.7, 9.15.1.10
    8 releases listed9.15.1, 9.15.1.1, 9.15.1.7, 9.15.1.10, 9.15.1.15, 9.15.1.16, 9.15.1.17, 9.15.1.21
    First fixed releaseNot published in the sources followed
  7. 9.14End of life
    Affected versions9.14.1, 9.14.1.6, 9.14.1.10, 9.14.1.15
    28 releases listed9.14.1, 9.14.1.6, 9.14.1.10, 9.14.1.15, 9.14.1.19, 9.14.1.30, 9.14.2, 9.14.2.4, 9.14.2.8, 9.14.2.13, 9.14.2.15, 9.14.3, 9.14.3.1, 9.14.3.9, 9.14.3.11, 9.14.3.13, 9.14.3.15, 9.14.3.18, 9.14.4, 9.14.4.6, 9.14.4.7, 9.14.4.12, 9.14.4.13, 9.14.4.14, 9.14.4.15, 9.14.4.17, 9.14.4.22, 9.14.4.23
    First fixed releaseNot published in the sources followed
  8. 9.12End of life
    Affected versions9.12.1, 9.12.1.2, 9.12.1.3, 9.12.2
    41 releases listed9.12.1, 9.12.1.2, 9.12.1.3, 9.12.2, 9.12.2.1, 9.12.2.4, 9.12.2.5, 9.12.2.9, 9.12.3, 9.12.3.2, 9.12.3.7, 9.12.3.9, 9.12.3.12, 9.12.4, 9.12.4.2, 9.12.4.4, 9.12.4.7, 9.12.4.8, 9.12.4.10, 9.12.4.13, 9.12.4.18, 9.12.4.24, 9.12.4.26, 9.12.4.29, 9.12.4.30, 9.12.4.35, 9.12.4.37, 9.12.4.38, 9.12.4.39, 9.12.4.40, 9.12.4.41, 9.12.4.47, 9.12.4.48, 9.12.4.50, 9.12.4.52, 9.12.4.54, 9.12.4.55, 9.12.4.56, 9.12.4.58, 9.12.4.62, 9.12.4.65
    First fixed releaseNot published in the sources followed
  9. 9.8End of life
    Affected versions9.8.1, 9.8.1.5, 9.8.1.7, 9.8.2
    49 releases listed9.8.1, 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, 9.8.2.33, 9.8.2.35, 9.8.2.38, 9.8.3, 9.8.3.8, 9.8.3.11, 9.8.3.14, 9.8.3.16, 9.8.3.18, 9.8.3.21, 9.8.3.26, 9.8.3.29, 9.8.4, 9.8.4.3, 9.8.4.7, 9.8.4.8, 9.8.4.10, 9.8.4.12, 9.8.4.15, 9.8.4.17, 9.8.4.20, 9.8.4.22, 9.8.4.25, 9.8.4.26, 9.8.4.29, 9.8.4.32, 9.8.4.33, 9.8.4.34, 9.8.4.35, 9.8.4.39, 9.8.4.40, 9.8.4.41, 9.8.4.43, 9.8.4.44, 9.8.4.45, 9.8.4.46, 9.8.4.48
    First fixed releaseNot published in the sources followed

The vendor states fixes are available; the releases per branch are in its advisory.

Cisco Firepower Threat Defense Software

Source: CVE-2024-20353cisco-sa-asaftd-websrvs-dos-X8gNucD2

  1. 7.4
    Affected versions7.4, 7.4.1
    First fixed releaseNot published in the sources followed
  2. 7.3
    Affected versions7.3, 7.3.1, 7.3.1.1
    First fixed releaseNot published in the sources followed
  3. 7.2
    Affected versions7.2, 7.2.0.1, 7.2.1, 7.2.2
    9 releases listed7.2, 7.2.0.1, 7.2.1, 7.2.2, 7.2.3, 7.2.4, 7.2.4.1, 7.2.5, 7.2.5.1
    First fixed releaseNot published in the sources followed
  4. 7.1End of life
    Affected versions7.1, 7.1.0.1, 7.1.0.2, 7.1.0.3
    First fixed releaseNot published in the sources followed
  5. 7.0
    Affected versions7.0, 7.0.0.1, 7.0.1, 7.0.1.1
    11 releases listed7.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.0.2.1, 7.0.3, 7.0.4, 7.0.5, 7.0.6, 7.0.6.1
    First fixed releaseNot published in the sources followed
  6. 6.7End of life
    Affected versions6.7, 6.7.0.1, 6.7.0.2, 6.7.0.3
    First fixed releaseNot published in the sources followed
  7. 6.6End of life
    Affected versions6.6, 6.6.0.1, 6.6.1, 6.6.3
    10 releases listed6.6, 6.6.0.1, 6.6.1, 6.6.3, 6.6.4, 6.6.5, 6.6.5.1, 6.6.5.2, 6.6.7, 6.6.7.1
    First fixed releaseNot published in the sources followed
  8. 6.4End of life
    Affected versions6.4, 6.4.0.1, 6.4.0.2, 6.4.0.3
    18 releases listed6.4, 6.4.0.1, 6.4.0.2, 6.4.0.3, 6.4.0.4, 6.4.0.5, 6.4.0.6, 6.4.0.7, 6.4.0.8, 6.4.0.9, 6.4.0.10, 6.4.0.11, 6.4.0.12, 6.4.0.13, 6.4.0.14, 6.4.0.15, 6.4.0.16, 6.4.0.17
    First fixed releaseNot published in the sources followed
  9. 6.2
    Affected versions6.2.3, 6.2.3.1, 6.2.3.2, 6.2.3.3
    19 releases listed6.2.3, 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, 6.2.3.9, 6.2.3.10, 6.2.3.11, 6.2.3.12, 6.2.3.13, 6.2.3.14, 6.2.3.15, 6.2.3.16, 6.2.3.17, 6.2.3.18
    First fixed releaseNot published in the sources followed

The vendor states fixes are available; the releases per branch are in its advisory.

Remediation

Fix available

Vendor fix

Cisco has released updates that fix this vulnerability; its advisory lists them.

SourceCisco Security Advisory cisco-sa-asaftd-websrvs-dos-X8gNucD2· revised 24 Apr 2024

Workarounds (vendor)

Cisco states in its advisory that no workaround is available.

SourceCisco Security Advisory cisco-sa-asaftd-websrvs-dos-X8gNucD2

CISA KEV required action

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

CISA due date:

SourceCISA KEV

Last verified 1 Oct 2026 at 13:37 UTC

Known exploitation

Added to CISA KEV on 24 Apr 2024

Federal remediation due date: 1 May 2024

The CISA required action is shown under Remediation.

71% probability of exploitation in the next 30 days (percentile 99%).

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CERT-FR

No CERT-FR advisory or alert of the last two years references this CVE, for the vendors Patcharo covers.

Timeline

  1. Added to CISA KEV
  2. Published by the source
  3. CISA remediation due date
  4. Source record last modified
  5. EPSS score computed
  6. Last verified by Patcharo

Official sources

References

Known exploited

Cisco · CISA Known Exploited Vulnerabilities · NVD · FIRST EPSS · Cisco Security Advisory cisco-sa-asaftd-websrvs-dos-X8gNucD2

How Patcharo reads this

Affected and fixed releases come from the vendor's structured statements and are matched against exact versions; CVSS from NVD, exploitation from CISA KEV and the vendor's own advisory, probability from FIRST EPSS. Missing data stays Unknown and never becomes Not affected.

Read the methodologyRead the guide: Cisco Secure Firewall release trains: Threat Defense, Management Center and ASA versions explained

Related vulnerabilities

Other records affecting the same products, newest first.

  • CVE-2026-20349Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service VulnerabilityHighKEV
  • CVE-2025-20362Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Missing Authorization VulnerabilityHighKEV
  • CVE-2025-20333Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow VulnerabilityCriticalKEV
  • CVE-2024-20481Cisco ASA and FTD Denial-of-Service VulnerabilityMediumKEV
  • CVE-2024-20359Cisco ASA and FTD Privilege Escalation VulnerabilityMediumKEV

All Secure Firewall ASA vulnerabilitiesAll Secure Firewall Threat Defense (FTD) vulnerabilitiesAll Cisco vulnerabilities