KEV Intelligence

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2024-20353

Cisco Adaptive Security Appliance (ASA) Software Denial of Service

Cisco / Cisco Adaptive Security Appliance (ASA) Software · 9.8.1 to <= 9.8.4.48

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Severity
CVSS 8.6 · High
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
70.7%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2024-20353 is an unauthenticated vulnerability affecting Cisco Cisco Adaptive Security Appliance (ASA) Software, Cisco Firepower Threat Defense.... A vulnerability in the management and VPN web servers for Cisco...

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Cisco / Cisco Adaptive Security Appliance (ASA) Software 9.8.1 to <= 9.8.4.48.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Cisco Adaptive Security Appliance (ASA) Software Denial of Service

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.

Vendor Product Affected Status
Cisco Cisco Firepower Threat Defense Software 6.6.0.1 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.1 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.3 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.4 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.5 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.5.1 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.5.2 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.7 Affected
Cisco Cisco Firepower Threat Defense Software 6.6.7.1 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.1 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.3 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.2 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.4 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.5 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.6 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.7 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.8 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.9 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.10 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.11 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.12 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.13 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.14 Affected
Cisco Cisco Firepower Threat Defense Software 6.4.0.15 Affected
Published
24 Apr 2024
Exploitation Reported
24 Apr 2024
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

nessus_scanner edge cisa

CVE References

  • CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2024-20353
  • cisco-sa-asaftd-websrvs-dos-X8gNucD2 sec.cloudapps.cisco.com · CVE Record https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurity...

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 24 Apr 2024

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source Added
CISA First 2024-04-24 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
0
User-Agents
0

Raw values available in Pro and Enterprise.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nessus https://www.tenable.com/plugins/nessus/193915 02 Jun 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

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

EPSS

70.7%

Weaknesses

Loop with Unreachable Exit Condition ('Infinite Loop') CWE-835

Timeline

From disclosure to observed exploitation

  1. Nessus plugin available

    Scanner coverage available

  2. CVE published

    Vulnerability disclosed publicly

  3. Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2024-20353

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2024-20353",
  "confidence": "Confirmed",
  "cvss_score": 8.6,
  "cvss_estimated": false,
  "epss_score": 0.70686,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

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