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Adaptive Security Appliance SoftwareApplication · Cisco

CVE-2019-12677

MEDIUM · 6.5 CVSS v3.1 Published 2019-10-02
Fix available
A fix is available. Upgrade to 9.1.7.4 / 9.2.4.8 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition that prevents the creation of new SSL/Transport Layer Security (TLS) connections to an affected device. The vulnerability is due to incorrect handling of Base64-encoded strings. An attacker could exploit this vulnerability by opening many SSL VPN sessions to an affected device. The attacker would need to have valid user credentials on the affected device to exploit this vulnerability. A successful exploit could allow the attacker to overwrite a special system memory location, which will eventually result in memory allocation errors for new SSL/TLS sessions to the device, preventing successful establishment of these sessions. A reload of the device is required to recover from this condition. Established SSL/TLS connections to the device and SSL/TLS connections through the device are not affected. Note: Although this vulnerability is in the SSL VPN feature, successful exploitation of this vulnerability would affect all new SSL/TLS sessions to the device, including management sessions.

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 memory corruption vulnerability in Cisco ASA SSL VPN feature allows authenticated attackers to cause DoS by opening many SSL VPN sessions. The flaw stems from improper handling of Base64-encoded strings, enabling overwriting of a special system memory location that causes memory allocation failures for subsequent SSL/TLS connections.

MitigationApply the Cisco security patch for CVE-2019-12677 to affected ASA software versions; schedule a maintenance window as device reload is required after patching.

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 SoftwareApplication
Affected:>= 9.3, < 9.3.3.9< 9.1.7.4>= 9.2, < 9.2.4.8>= 9.4, < 9.4.2.11>= 9.5, < 9.5.2.5>= 9.6, < 9.6.2

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/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 version
    Log into the ASA CLI and run 'show version' to display the software version. Look for 'Cisco Adaptive Security Appliance' in the output and note the version number (for example, 9.4.1).
    Affected if The device is a Cisco ASA running a version that falls within any of these ranges: 9.3.x before 9.3.3.9, any 9.1.x before 9.1.7.4, 9.2.x before 9.2.4.8, 9.4.x before 9.4.2.11, 9.5.x before 9.5.2.5, or 9.6.x before 9.6.2.
  2. Confirm SSL VPN feature is configured
    Run 'show vpn-sessiondb' or 'show webvpn' in the ASA CLI to check if any SSL VPN configurations (including AnyConnect, clientless, or site-to-site VPN using SSL) exist on the device.
    Affected if SSL VPN is actively configured or has been used on the device, as the vulnerability is triggered through the SSL VPN feature.
  3. Check for memory allocation failures
    Run 'show memory' and 'show processes memory' periodically or review syslog messages for indications of memory allocation failures, particularly after periods of high SSL VPN session activity.
    Affected if Memory allocation failures occur for new SSL/TLS connections, especially after multiple SSL VPN sessions have been opened, which may indicate exploitation of this memory corruption flaw.
  4. Review SSL VPN session history
    Run 'show vpn-sessiondb detail' or check syslog entries for patterns of unusually high numbers of SSL VPN session establishments that may have preceded connection failures.
    Affected if The device shows signs of SSL VPN sessions causing subsequent connection failures, which aligns with the DoS behavior described in this vulnerability.

You are affected if you run a Cisco ASA with SSL VPN enabled and the software version falls within any of the vulnerable version ranges listed, particularly if you observe memory allocation failures for new SSL/TLS connections after periods of SSL VPN activity.

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
Upgrade available Upgrade to 9.1.7.4 / 9.2.4.8 / 9.3.3.9 or later
Fixed in 9.1.7.49.2.4.89.3.3.9
Interim mitigation

Apply the Cisco security patch for CVE-2019-12677 to affected ASA software versions; schedule a maintenance window as device reload is required after patching.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,880
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Scan for this in your stack

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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-2019-12677 in production — separate from our analysis above.

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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
  • No weaponised exploit code, or anything meant to cause harm
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