dbcve.org
Ios XeOperating system · Cisco

CVE-2018-0157

HIGH · 8.6 CVSS v3.1 Published 2018-03-28
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 Zone-Based Firewall code of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a device to reload. The vulnerability is due to the way fragmented packets are handled in the firewall code. An attacker could exploit this vulnerability by sending fragmented IP Version 4 or IP Version 6 packets through an affected device. An exploit could allow the attacker to cause the device to crash, resulting in a denial of service (DoS) condition. The following releases of Cisco IOS XE Software are vulnerable: Everest-16.4.1, Everest-16.4.2, Everest-16.5.1, Everest-16.5.1b, Everest-16.6.1, Everest-16.6.1a. Cisco Bug IDs: CSCvf60296.

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 vulnerability in the Zone-Based Firewall code of Cisco IOS XE Software allows an unauthenticated remote attacker to cause device reload by sending specially crafted fragmented IPv4 or IPv6 packets through an affected device. The vulnerability stems from improper handling of fragmented packets in the firewall code, leading to a denial of service condition.

MitigationApply the appropriate Cisco IOS XE software update to a non-vulnerable version. If immediate patching is not feasible, consider filtering fragmented packets at network perimeter devices as a temporary mitigation.

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
Affected:= 16.4.1= 16.4.2= 16.5.1= 16.5.1b= 16.6.1= 16.6.1a

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 the Cisco IOS XE version
    Use the command 'show version' or 'show version | include Version' to display the installed IOS XE software version
    Affected if The displayed version matches 16.4.1, 16.4.2, 16.5.1, 16.5.1b, 16.6.1, or 16.6.1a
  2. Confirm Zone-Based Firewall is enabled
    Use the command 'show zone-pair security' to list configured zone-based firewall policy pairs
    Affected if Any zone-pair security policies are configured and active, indicating ZBFW is enabled on the device
  3. Verify firewall inspection is active for IP traffic
    Use the command 'show policy-map type inspect zone-pair' to inspect the active policy maps applied to zone-pairs
    Affected if The policy maps show inspection rules for IPv4 or IPv6 traffic applied to active zone-pairs
  4. Check for active interface assignments to security zones
    Use the command 'show zone-member security' to display interfaces assigned to security zones
    Affected if Interfaces are assigned to security zones and those zones are part of a zone-pair with an inspect policy

The device is affected if it runs IOS XE versions 16.4.1, 16.4.2, 16.5.1, 16.5.1b, 16.6.1, or 16.6.1a AND has Zone-Based Firewall with active inspect policies applied to zone-pairs processing IPv4 or IPv6 traffic.

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 appropriate Cisco IOS XE software update to a non-vulnerable version. If immediate patching is not feasible, consider filtering fragmented packets at network perimeter devices as a temporary mitigation.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2018-0157 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
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