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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2026-20103

HIGH · 8.6 CVSS v3.1 Published 2026-03-04
Fix available
A fix is available. Upgrade to 7.0.9 / 7.2.11 or later.
See remediation →
95/100
Remediation priority · Urgent
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 Remote Access SSL VPN functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust device memory resulting in a denial of service (DoS) condition to new Remote Access SSL VPN connections. This does not affect the management interface, though it may become temporarily unresponsive. This vulnerability is due to trusting user input without validation. An attacker could exploit this vulnerability by sending crafted packets to the Remote Access SSL VPN server. A successful exploit could allow the attacker to cause the device web interface to stop responding, resulting in a 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

A memory exhaustion vulnerability exists in Cisco ASA and FTD Remote Access SSL VPN functionality. An unauthenticated remote attacker can send crafted packets to the VPN server that cause excessive memory consumption, leading to denial of service for new VPN connections. The vulnerability stems from improper validation of user-supplied input.

MitigationApply the vendor patch from Cisco for this vulnerability. As a temporary workaround, consider implementing rate limiting or access controls on the VPN interface to reduce attack surface until the patch can be deployed.

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
Adaptive Security Appliance SoftwareOperating system
Affected:>= 9.12.1, < 9.16.4.85>= 9.17.1, < 9.18.4.66>= 9.19.1, < 9.20.4>= 9.22.1.1, < 9.22.2.4>= 9.23.1, < 9.23.1.7
Secure Firewall Threat DefenseApplication
Affected:>= 6.4.0, < 7.0.9>= 7.1.0, < 7.2.11>= 7.3.0, < 7.4.3>= 7.6.0, < 7.6.4>= 7.7.0, < 7.7.11

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
Changed
Confidentiality
None
Integrity
None
Availability
High

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

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 Cisco device product type
    Run 'show version' or 'show inventory' on the device CLI to confirm whether it is running Cisco ASA Software or Cisco Firepower Threat Defense (FTD) Software.
    Affected if The device is not an ASA or FTD device - this CVE only applies to those platforms.
  2. Determine the installed ASA software version
    On ASA devices, run 'show version' and locate the 'Adaptive Security Appliance Software Version' line. Compare this version number against the affected ranges: >= 9.12.1 and < 9.16.4.85; >= 9.17.1 and < 9.18.4.66; >= 9.19.1 and < 9.20.4; >= 9.22.1.1 and < 9.22.2.4; >= 9.23.1 and < 9.23.1.7
    Affected if The installed version falls within any of these ranges.
  3. Determine the installed FTD software version
    On FTD devices, run 'show version' and locate the 'Cisco Firepower Threat Defense Software' version line. Compare this version number against the affected ranges: >= 6.4.0 and < 7.0.9; >= 7.1.0 and < 7.2.11; >= 7.3.0 and < 7.4.3; >= 7.6.0 and < 7.6.4; >= 7.7.0 and < 7.7.11
    Affected if The installed version falls within any of these ranges.
  4. Verify if Remote Access SSL VPN is enabled
    Run 'show vpn-sessiondb' or 'show run webvpn' on ASA, or 'show vpn-sessiondb' on FTD to check for active or configured SSL VPN remote access tunnels. Also check 'show run | include webvpn' or 'show run | include ssl vpn' to see if any SSL VPN configuration exists.
    Affected if Remote Access SSL VPN functionality is configured or active on the device - the vulnerability only triggers when this feature is exposed.
  5. Monitor current memory utilization
    Run 'show memory' on ASA or FTD to check current memory allocation. Compare the used memory against available memory and note any unusually high consumption that could indicate active exploitation or prior attacks.
    Affected if Memory utilization is abnormally high, especially if new VPN connections are failing or being rejected.

The environment is affected if the device runs Cisco ASA or FTD software with an installed version within the affected ranges AND Remote Access SSL VPN functionality is enabled and exposed.

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
Upgrade available Upgrade to 7.0.9 / 7.2.11 / 7.4.3 or later
Fixed in 7.0.97.2.117.4.3
Interim mitigation

Apply the vendor patch from Cisco for this vulnerability. As a temporary workaround, consider implementing rate limiting or access controls on the VPN interface to reduce attack surface until the patch can be deployed.

Recommended fix High confidence

ASA: 9.16.4.85, 9.18.4.66, 9.20.4, or 9.22.2.4 (depending on current branch); FTD: 7.0.9, 7.2.11, 7.4.3, or 7.6.4 (depending on current branch)

  1. 1. Identify the currently installed Cisco ASA or FTD software version using 'show version' command
  2. 2. For ASA Software: Upgrade to version 9.16.4.85 or later if running 9.12.1 - 9.16.x
  3. 3. For ASA Software: Upgrade to version 9.18.4.66 or later if running 9.17.1 - 9.18.x
  4. 4. For ASA Software: Upgrade to version 9.20.4 or later if running 9.19.1 - 9.20.x
  5. 5. For ASA Software: Upgrade to version 9.22.2.4 or later if running 9.22.1.1 - 9.22.x
  6. 6. For FTD Software: Upgrade to version 7.0.9 or later if running 6.4.0 - 7.0.x
  7. 7. For FTD Software: Upgrade to version 7.2.11 or later if running 7.1.0 - 7.2.x
  8. 8. For FTD Software: Upgrade to version 7.4.3 or later if running 7.3.0 - 7.4.x
Caveat Standard Cisco upgrade considerations apply - review Cisco release notes for any VPN configuration changes, and test in staging environment before production deployment

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

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2026-20103 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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