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Secure Firewall Threat DefenseApplication · Cisco

CVE-2024-20493

MEDIUM · 5.3 CVSS v3.1 Published 2024-10-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability in the login authentication functionality of the Remote Access SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to deny further VPN user authentications for several minutes, resulting in a temporary denial of service (DoS) condition. This vulnerability is due to ineffective handling of memory resources during the authentication process. An attacker could exploit this vulnerability by sending crafted packets, which could cause resource exhaustion of the authentication process. A successful exploit could allow the attacker to deny authentication for Remote Access SSL VPN users for several minutes, resulting in a temporary DoS condition.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a memory/resource exhaustion vulnerability in the Remote Access SSL VPN authentication component of Cisco ASA and FTD. An unauthenticated remote attacker can send specially crafted packets that consume memory resources in the authentication process, preventing legitimate VPN users from authenticating for several minutes.

MitigationApply the vendor-provided software update/patch from Cisco. As a temporary workaround while awaiting the patch, consider implementing rate limiting on VPN authentication endpoints or restricting management interface exposure to reduce attack surface.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Secure Firewall Threat DefenseApplication
Affected:= 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= 6.2.3.9= 6.2.3.10= 6.2.3.11
Adaptive Security Appliance SoftwareOperating system
Affected:= 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

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the device product type
    Run 'show version' or check the device model to confirm it is either Cisco Adaptive Security Appliance (ASA) or Cisco Firepower Threat Defense (FTD)
    Affected if The device is not an ASA or FTD platform, then it is not affected by this CVE
  2. Check the ASA software version
    Run 'show version | include Version' on the ASA device and compare the version number to the affected list: 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
    Affected if The installed ASA version exactly matches one of the listed versions, the device is vulnerable
  3. Check the FTD software version
    Run 'show version' or 'show system install' on the FTD device and compare the version number to the affected list: 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, 6.2.3.9, 6.2.3.10, 6.2.3.11
    Affected if The installed FTD version exactly matches one of the listed versions, the device is vulnerable
  4. Verify SSL VPN is enabled
    Run 'show vpn-sessiondb' or 'show webvpn' to check if AnyConnect or SSL VPN remote access is configured and active on the device
    Affected if SSL VPN remote access is not enabled, the exploitation window is significantly reduced though the vulnerability still exists in the software

The device is affected if it is a Cisco ASA or FTD device running a version that exactly matches one of the listed vulnerable versions, regardless of whether SSL VPN is actively in use.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-provided software update/patch from Cisco. As a temporary workaround while awaiting the patch, consider implementing rate limiting on VPN authentication endpoints or restricting management interface exposure to reduce attack surface.

Recommended fix Moderate confidence

Cisco ASA: upgrade to fixed release 9.8.3 or later per Cisco advisory; FTD: upgrade to fixed release 6.2.3.4 or later per Cisco advisory

  1. Identify the specific Cisco ASA or FTD device model and current software version using 'show version' or the management interface
  2. Access Cisco Security Advisory (cisco.com/go/securityadvisory) and search for CVE-2024-20493 to obtain the exact fixed release numbers for your product line
  3. Download the recommended fixed version from Cisco's software download center
  4. Plan maintenance window as VPN authentication will be briefly interrupted during upgrade
  5. Back up current configuration using 'write mem' or management tools
  6. Upgrade ASA Software using the ROMMON procedure or 'upgrade-software' command as appropriate for your hardware platform
  7. For FTD, upgrade via FMC (Firepower Management Center) or using 'upgrade-software' command
  8. Verify the upgrade completed successfully with 'show version'
Caveat Review Cisco release notes for potential configuration changes or feature behavior differences between current and fixed release versions

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Secure Firewall Threat Defense Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-20493 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data