Ios XeOperating system · Cisco
CVE-2019-12666
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 · uneditedA vulnerability in the Guest Shell of Cisco IOS XE Software could allow an authenticated, local attacker to perform directory traversal on the base Linux operating system of Cisco IOS XE Software. The vulnerability is due to incomplete validation of certain commands. An attacker could exploit this vulnerability by first accessing the Guest Shell and then entering specific commands. A successful exploit could allow the attacker to execute arbitrary code on the base Linux operating system.
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 confidenceA directory traversal vulnerability in Cisco IOS XE Guest Shell feature allows an authenticated local attacker with Guest Shell access to escape the Linux container and execute arbitrary code on the underlying host operating system. The vulnerability stems from incomplete validation of certain commands entered within the Guest Shell environment.
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
Ios XeOperating system
>= 16.4, < 16.6.5>= 16.7, < 16.9.3= 16.11.1CVSS 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
- Local
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Verify Cisco IOS XE version is within affected rangeExecute 'show version' or 'show version | include Version' to display the running IOS XE version. Compare the version number to: 16.4 through 16.6.4, 16.7 through 16.9.2, or 16.11.1Affected if The displayed version falls within any of these ranges: >= 16.4 and < 16.6.5, >= 16.7 and < 16.9.3, or equals exactly 16.11.1
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Confirm Guest Shell feature is enabledExecute 'guestshell status' or 'show guestshell' to determine if the Guest Shell Linux container is active on the deviceAffected if Guest Shell is enabled and running on the device
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Check for suspicious Guest Shell process activityReview output of 'guestshell exec ps aux' or 'guestshell run ps aux' to list processes running inside the Guest Shell container. Look for unexpected or unauthorized processesAffected if Unfamiliar processes are observed running inside Guest Shell that were not authorized by administrators
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Audit Guest Shell access logsExecute 'show logging | include guestshell' or review syslog/buffered logs for entries containing 'guestshell' to identify access patterns and any escape-related errors or anomaliesAffected if Log entries show unauthorized Guest Shell access attempts or unusual command patterns that may indicate exploitation attempts
The device is affected if it runs a vulnerable IOS XE version within the specified ranges AND has Guest Shell enabled, as the attacker requires Guest Shell access to exploit the directory traversal vulnerability.
Generated from the published advisory. Verify against your own configuration.
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 data16.6.516.9.3
Apply Cisco IOS XE software updates when available; restrict Guest Shell access to only necessary personnel; monitor for unauthorized Guest Shell access attempts.
Fix this in Ios Xe
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-12666 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-12666 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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