dbcve.org
Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 15 Apr 2022.
iOSOperating system · Cisco

CVE-2017-3881

CRITICAL · 9.8 CVSS v3.1 Published 2017-03-17
Fix available
A fix is available. Upgrade to after 15.1 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Public exploit 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 Cisco Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a reload of an affected device or remotely execute code with elevated privileges. The Cluster Management Protocol utilizes Telnet internally as a signaling and command protocol between cluster members. The vulnerability is due to the combination of two factors: (1) the failure to restrict the use of CMP-specific Telnet options only to internal, local communications between cluster members and instead accept and process such options over any Telnet connection to an affected device; and (2) the incorrect processing of malformed CMP-specific Telnet options. An attacker could exploit this vulnerability by sending malformed CMP-specific Telnet options while establishing a Telnet session with an affected Cisco device configured to accept Telnet connections. An exploit could allow an attacker to execute arbitrary code and obtain full control of the device or cause a reload of the affected device. This affects Catalyst switches, Embedded Service 2020 switches, Enhanced Layer 2 EtherSwitch Service Module, Enhanced Layer 2/3 EtherSwitch Service Module, Gigabit Ethernet Switch Module (CGESM) for HP, IE Industrial Ethernet switches, ME 4924-10GE switch, RF Gateway 10, and SM-X Layer 2/3 EtherSwitch Service Module. Cisco Bug IDs: CSCvd48893.

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 critical vulnerability in Cisco IOS and IOS XE Software allows remote attackers to execute arbitrary code or cause device reloads via malformed Cluster Management Protocol (CMP) Telnet options. The CMP incorrectly processes Telnet options received over any Telnet connection rather than restricting them to internal cluster communications, enabling unauthenticated remote code execution with elevated privileges.

MitigationDisable Telnet access on affected devices and use SSH for management instead; apply Cisco patches for CVE-2017-3881 (CSCvd48893) to all affected Cisco IOS/IOS XE devices.

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
iOSOperating system
Affected:>= 12.2s, <= 15.1\(3\)svs
Ios XeOperating system
Affected:>= 3.2sg, <= 3.9e

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Cisco IOS or IOS XE version
    Run 'show version' and locate the 'IOS (tm)' or 'IOS XE' version string in the output. Compare the full version number (e.g., 15.1(3)sv) against the affected ranges: IOS >= 12.2s through 15.1(3)svs, or IOS XE >= 3.2sg through 3.9e.
    Affected if The running version falls within or below these ranges and has not been patched beyond the fix for CSCvd48893.
  2. Verify if Telnet is enabled on the device
    Run 'show running-config | include transport input' or examine VTY lines with 'show line vty 0 4'. Look for 'transport input telnet' or 'transport input all' in the VTY configuration.
    Affected if Telnet is enabled as an allowed input protocol on any VTY line (including 'transport input all' which includes telnet).
  3. Check for active Telnet listeners
    Run 'show control-plane host open-port' or 'show sockets binding' to identify if TCP port 23 is in a listening state. Alternatively, check if 'telnet' commands are accepted on any interface.
    Affected if The device is actively listening on TCP port 23 (Telnet) for remote management connections.
  4. Determine if Cluster Management Protocol (CMP) is configured
    Run 'show running-config | include cluster' or check for 'cluster' keywords in the configuration. Also check 'show version' output for cluster-related features.
    Affected if The device is configured for clustering, which enables CMP processing on Telnet connections.

A device is affected if it runs a vulnerable IOS/IOS XE version within the specified ranges AND has Telnet enabled and accessible, particularly if CMP/cluster features are present, as the flaw requires malformed CMP Telnet options to be processed on an active Telnet connection.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 15.1
Interim mitigation

Disable Telnet access on affected devices and use SSH for management instead; apply Cisco patches for CVE-2017-3881 (CSCvd48893) to all affected Cisco IOS/IOS XE devices.

Recommended fix High confidence

Upgrade to a fixed Cisco IOS/IOS XE release as specified in the Cisco Security Advisory for your platform and release train (e.g., 15.2(4)E5, 15.5(3)T2, 16.2.1, or later releases in your train)

  1. 1. Identify the exact Cisco IOS or IOS XE version currently running on the device using 'show version' command.
  2. 2. Access the Cisco Security Advisories portal and search for Cisco IOS and IOS XE Security Advisory for CVE-2017-3881 (CSCvd48893).
  3. 3. Determine the recommended fixed release for your specific platform and release train from the advisory.
  4. 4. Download the appropriate fixed Cisco IOS or IOS XE software from Cisco's download portal (requires valid service contract).
  5. 5. Upload the new software image to the device using TFTP, FTP, or SCP.
  6. 6. Configure the device to boot from the new image using 'boot system <flash:|http:><filename>' command.
  7. 7. Reload the device to apply the new software version.
  8. 8. As a secondary mitigation, disable Telnet access and enforce SSH only using 'transport input ssh' under line vty configurations.
Caveat Ensure compatibility with other Cisco devices in the cluster; some legacy cluster configurations may require updates after disabling Telnet

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in iOS Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
Get it fixed fast

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 locally
dbcve dependency scanner

Check whether your project pulls in CVE-2017-3881 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2017-3881 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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