Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2024-20353

Cisco Adaptive Security Appliance (ASA) Software Denial of Service

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

Watch CVE-2024-20353 Browse KEV feed
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 Adaptive Security Appliance (ASA) Software, Cisco Firepower Threat Defense Software. A vulnerability in the management and VPN web servers for Cisco...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV.

Who is affected?

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.

cisco Affected
asa
Through 9.8.4.48 Through 9.12.4.65 Before 9.14.4.23 Through 9.15.1.21 Through 9.16.4.55 Through 9.17.1.33 Through 9.18.4.8 Through 9.19.1.27 Through 9.20.2
cisco Affected
firepower_threat_defense_software
Through 6.2.3.18 Through 6.6.7.1 Through 6.4.0.17 Through 6.7.0.3 Through 7.0.6 Through 7.1.0.3 Through 7.2.4.1 Through 7.3.1.1 Through 7.4.1
Cisco Affected
Cisco Adaptive Security Appliance (ASA) Software
9.8.1 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 9.8.3.8 9.8.3.11 9.8.3.14 9.8.3.16 9.8.3.18 9.8.3.21 9.8.3 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 9.8.4.25 9.8.4.20 9.8.4.22 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 9.12.1 9.12.1.2 9.12.1.3 9.12.2 9.12.2.4 9.12.2.5 9.12.2.9 9.12.3 9.12.3.2 9.12.3.7 9.12.4 9.12.3.12 9.12.3.9 9.12.2.1 9.12.4.2 9.12.4.4 9.12.4.7 9.12.4.10 9.12.4.13 9.12.4.8 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 9.14.1 9.14.1.10 9.14.1.6 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 9.14.3.18 9.14.3.15 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 9.15.1 9.15.1.7 9.15.1.10 9.15.1.15 9.15.1.16 9.15.1.17 9.15.1.1 9.15.1.21 9.16.1 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 9.17.1 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 9.18.1 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 9.19.1 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 9.20.1 9.20.1.5 9.20.2
Cisco Affected
Cisco Firepower Threat Defense Software
6.2.3 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 6.2.3.10 6.2.3.11 6.2.3.9 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 6.6.0 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 6.4.0 6.4.0.1 6.4.0.3 6.4.0.2 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 6.7.0 6.7.0.1 6.7.0.2 6.7.0.3 7.0.0 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 7.1.0 7.1.0.1 7.1.0.2 7.1.0.3 7.2.0 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 7.3.0 7.3.1 7.3.1.1 7.4.0 7.4.1
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 Previdian 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

A trusted third party reported exploitation.

Known exploited vulnerability sources

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

Learn about Pro API access
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
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian 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

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

70.7%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

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

Timeline

From disclosure to observed exploitation

  1. 09:26 UTC

    Nessus plugin available

    Scanner coverage available

  2. 18:15 UTC

    CVE published

    Vulnerability disclosed publicly

  3. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. 15:08 UTC

    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.

Start 14-day Pro trial Read API docs
  • 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

Sample API response 
{
  "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 }
}