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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2018-0251

MEDIUM · 6.1 CVSS v3.0 Published 2018-04-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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 Web Server Authentication Required screen of the Clientless Secure Sockets Layer (SSL) VPN portal of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a user of that portal on an affected device. The vulnerability is due to insufficient validation of user-supplied input by the web-based interface of an affected device. An attacker could exploit this vulnerability by persuading a user of the interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the portal or allow the attacker to access sensitive browser-based information. This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco ASA Software: 3000 Series Industrial Security Appliances, Adaptive Security Virtual Appliance (ASAv), ASA 5500 Series Adaptive Security Appliances, ASA 5500-X Series Next-Generation Firewalls, ASA Services Module for Cisco Catalyst 6500 Series Switches, ASA Services Module for Cisco 7600 Series Routers. Cisco Bug IDs: CSCvh20742.

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

Cross-site scripting (XSS) vulnerability in the Web Server Authentication Required screen of Cisco ASA SSL VPN portal allows unauthenticated remote attackers to inject malicious script via crafted links. The root cause is insufficient validation of user-supplied input in the web interface. Successful exploitation enables arbitrary script execution in the context of the portal or access to sensitive browser-based information.

MitigationUpdate Cisco ASA Software to a patched release that addresses this vulnerability. If immediate patching is not feasible, implement URL filtering and user awareness training to mitigate phishing attempts leveraging this XSS vector.

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:= 9.8\(2.15\)= 9.9\(1\)

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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 the device is a Cisco Adaptive Security Appliance
    Run 'show version' and look for 'Cisco Adaptive Security Appliance' in the output
    Affected if The device is not a Cisco ASA appliance, then this CVE does not apply
  2. Check the ASA software version
    Run 'show version' and locate the version string (for example 9.8(2.15) or 9.9(1))
    Affected if The installed version exactly matches 9.8(2.15) or 9.9(1)
  3. Verify if WebVPN/SSL VPN portal is enabled
    Run 'show run webvpn' or 'show run | include webvpn' to check for active VPN portal configuration
    Affected if WebVPN or SSL VPN portal is enabled and the ASA version matches the affected versions listed above
  4. Check for remote access VPN configuration
    Run 'show run | include tunnel-group' or 'show run ssl' to identify SSL VPN-related settings
    Affected if SSL VPN or AnyConnect features are configured on the appliance

A Cisco ASA appliance running exactly version 9.8(2.15) or 9.9(1) with WebVPN/SSL VPN portal enabled is affected by this XSS vulnerability.

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

Update Cisco ASA Software to a patched release that addresses this vulnerability. If immediate patching is not feasible, implement URL filtering and user awareness training to mitigate phishing attempts leveraging this XSS vector.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
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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-2018-0251 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