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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2017-6608

HIGH · 8.6 CVSS v3.0 Published 2017-04-20
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 Secure Sockets Layer (SSL) and Transport Layer Security (TLS) code of Cisco ASA Software could allow an unauthenticated, remote attacker to cause a reload of the affected system. The vulnerability is due to improper parsing of crafted SSL or TLS packets. An attacker could exploit this vulnerability by sending a crafted packet to the affected system. Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed and transparent firewall mode and in single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic. A valid SSL or TLS session is needed to exploit this vulnerability. This vulnerability affects Cisco ASA Software running on the following products: Cisco ASA 1000V Cloud Firewall, Cisco ASA 5500 Series Adaptive Security Appliances, Cisco ASA 5500-X Series Next-Generation Firewalls, Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, Cisco Adaptive Security Virtual Appliance (ASAv), Cisco Firepower 9300 ASA Security Module, Cisco ISA 3000 Industrial Security Appliance. Fixed versions: 8.4(7.31) 9.0(4.39) 9.1(7) 9.2(4.6) 9.3(3.8) 9.4(2) 9.5(2). Cisco Bug IDs: CSCuv48243.

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 denial of service vulnerability in Cisco ASA Software's SSL/TLS packet parsing allows an unauthenticated remote attacker to cause system reload by sending crafted SSL/TLS packets. A valid SSL/TLS session is required, and only traffic directed to the affected system can trigger the exploit.

MitigationApply the fixed Cisco ASA Software versions (8.4(7.31), 9.0(4.39), 9.1(7), 9.2(4.6), 9.3(3.8), 9.4(2), 9.5(2) or later) or implement network-level filtering to block malformed SSL/TLS packets.

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:= 9.0.1= 9.0.2= 9.0.2.10= 9.0.3= 9.0.3.6= 9.0.3.8= 9.0.4= 9.0.4.1= 9.0.4.5= 9.0.4.7= 9.0.4.17= 9.0.4.20

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:3.0/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. Confirm Cisco ASA is in use
    Identify the device type and confirm it is running Cisco Adaptive Security Appliance (ASA) Software. This can be done via the 'show version' command or by reviewing device inventory.
    Affected if The device is not a Cisco ASA appliance, the check does not apply.
  2. Retrieve the ASA software version
    Execute 'show version' on the ASA CLI or obtain the version from the device management interface. Note the full version string including build number.
    Affected if The installed version matches one of the affected versions: 9.0.1, 9.0.2, 9.0.2.10, 9.0.3, 9.0.3.6, 9.0.3.8, 9.0.4, 9.0.4.1, 9.0.4.5, 9.0.4.7, 9.0.4.17, or 9.0.4.20.
  3. Verify SSL/TLS is enabled
    Check if the ASA has SSL/TLS services configured. Use 'show running-config' and look for ssl, tls, or webvpn-related configuration. Also check 'show interface' for any SSL-enabled interfaces.
    Affected if SSL/TLS services are enabled on the device (the vulnerability requires a valid SSL/TLS session to be exploited).
  4. Check if the device accepts SSL/TLS connections
    Review access lists and service policies to determine if inbound SSL/TLS traffic to the ASA is permitted. Use 'show access-list' and examine NAT/exemption rules.
    Affected if The ASA accepts SSL/TLS connections from external or untrusted networks (the flaw is triggered by crafted packets sent to the affected system).

You are affected if you are running any of the listed Cisco ASA versions (9.0.1 through 9.0.4.20 specific builds) AND have SSL/TLS services enabled and reachable on the device.

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 fixed Cisco ASA Software versions (8.4(7.31), 9.0(4.39), 9.1(7), 9.2(4.6), 9.3(3.8), 9.4(2), 9.5(2) or later) or implement network-level filtering to block malformed SSL/TLS packets.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,780
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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-2017-6608 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data