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Ios XeOperating system · Cisco

CVE-2017-3856

HIGH · 7.5 CVSS v3.0 Published 2017-03-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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 web user interface of Cisco IOS XE 3.1 through 3.17 could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient resource handling by the affected software when the web user interface is under a high load. An attacker could exploit this vulnerability by sending a high number of requests to the web user interface of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. To exploit this vulnerability, the attacker must have access to the management interface of the affected software, which is typically connected to a restricted management network. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software, if the web user interface of the software is enabled. By default, the web user interface is not enabled. Cisco Bug IDs: CSCup70353.

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 web user interface of Cisco IOS XE 3.1 through 3.17 exists due to insufficient resource handling when the web UI is under high load. An unauthenticated remote attacker can cause a denial of service by sending a high number of requests to the web UI, forcing the affected device to reload.

MitigationDisable the web user interface if not required (default state), or restrict access to the management interface via ACLs to the management network. Cisco recommends upgrading to a fixed release; if upgrading is not possible, ensure the web UI is disabled.

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:= 3.1.0s= 3.1.0sg= 3.1.1s= 3.1.1sg= 3.1.2s= 3.1.3as= 3.1.3s= 3.1.4as= 3.1.4s= 3.1s= 3.1sg= 3.2.0ja

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/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. Verify IOS XE version
    Run 'show version' or 'show version | include Version' to identify the installed IOS XE release
    Affected if The version falls within 3.1.0s through 3.17.x (any 3.1x, 3.2x through 3.17x release)
  2. Confirm web UI is enabled
    Run 'show ip http server status' or 'show running-config | include ip http server' to check if the HTTP server feature is active
    Affected if HTTP server or HTTPS server is enabled (status shows 'enabled' or config contains 'ip http server'/'ip http secure-server')
  3. Check web UI management access
    Run 'show interfaces' and review management interface configuration to determine if the web UI is accessible from external networks
    Affected if Management interface (typically GigabitEthernet0/0) is configured with an IP address and accessible without ACL restrictions

The device is affected if it runs IOS XE 3.1 through 3.17 AND has the web UI (HTTP/HTTPS server) enabled and accessible.

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

Disable the web user interface if not required (default state), or restrict access to the management interface via ACLs to the management network. Cisco recommends upgrading to a fixed release; if upgrading is not possible, ensure the web UI is disabled.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
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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-2017-3856 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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  • No spam, self-promotion, credentials, or personal data