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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2020-27124

HIGH · 8.6 CVSS v3.1 Published 2024-11-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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 SSL/TLS handler of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause the affected device to reload unexpectedly, leading to a denial of service (DoS) condition. The vulnerability is due to improper error handling on established SSL/TLS connections. An attacker could exploit this vulnerability by establishing an SSL/TLS connection with the affected device and then sending a malicious SSL/TLS message within that connection. A successful exploit could allow the attacker to cause the device to reload.Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

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 · high confidence

A high-severity denial-of-service vulnerability exists in Cisco ASA Software's SSL/TLS handler. The flaw stems from improper error handling when processing SSL/TLS messages on established connections. An unauthenticated remote attacker can trigger the vulnerability by establishing an SSL/TLS connection with the ASA and sending a specifically crafted malicious SSL/TLS message, causing the device to reload unexpectedly.

MitigationApply the Cisco ASA software update that addresses this vulnerability. There are no available workarounds, so updating to a patched version is the only remediation path.

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:= 9.13.1.12= 9.13.1.13= 9.14.1.10

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 Cisco ASA device and software version
    Log into the ASA CLI and run the command 'show version' to display the running software version. Look for the Adaptive Security Appliance Software version number in the output.
    Affected if The displayed software version is 9.13.1.12, 9.13.1.13, or 9.14.1.10, or falls within the same minor release branch as these versions.
  2. Confirm SSL/TLS services are enabled
    In the ASA CLI, run 'show service-policy' to see if SSL/TLS proxy services are configured. Also run 'show run all ssl' to display SSL configuration settings.
    Affected if SSL/TLS services (such as SSL VPN, SSL inspection, or TLS proxy) are enabled on the device.
  3. Review recent system logs for unexpected reloads
    Execute 'show crashinfo' or 'show reboot' in the ASA CLI to view recent system reloads. Check if any reloads occurred without an administrative cause.
    Affected if The device has experienced unexpected reloads that cannot be attributed to administrative actions or power issues.
  4. Check for SSL/TLS related error messages
    Use 'show log' or 'show logging buffered' to review system logs for SSL/TLS error messages, particularly those indicating malformed SSL/TLS messages or connection errors occurring around the time of any incidents.
    Affected if SSL/TLS error messages appear in the logs indicating processing failures on established connections.

A Cisco ASA device is affected if it runs a vulnerable ASA Software version (9.13.1.12, 9.13.1.13, or 9.14.1.10 or same branch) and has SSL/TLS services enabled, as the vulnerability is triggered by malicious SSL/TLS messages on established connections.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Cisco ASA software update that addresses this vulnerability. There are no available workarounds, so updating to a patched version is the only remediation path.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2020-27124 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
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  • Version or environment caveats, and links to real fixes
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