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iOSOperating system · Cisco

CVE-2019-12656

HIGH · 7.5 CVSS v3.1 Published 2019-09-25
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 IOx application environment of multiple Cisco platforms could allow an unauthenticated, remote attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a denial of service (DoS) condition. The vulnerability is due to a Transport Layer Security (TLS) implementation issue. An attacker could exploit this vulnerability by sending crafted TLS packets to the IOx web server on an affected device. A successful exploit could allow the attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a DoS condition.

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 · moderate confidence

A vulnerability in Cisco's IOx application environment allows an unauthenticated remote attacker to send crafted TLS packets to the IOx web server, causing it to stop processing HTTPS requests and resulting in a denial of service. The flaw is in the TLS implementation itself, not a configuration issue.

MitigationApply the appropriate Cisco firmware update for the IOx application environment on affected platforms. If patching is not immediately possible, consider network-level filtering to restrict exposure of the IOx management interface.

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:= 1.6.0.0= 1.8.0
Industrial Ethernet 2000 Series FirmwareOperating system
Affected:= 15.2\(6\)e
Ic3000 FirmwareOperating system
Affected:all versions
Ie 4000 FirmwareOperating system
Affected:all versions
Cgr 1000 FirmwareOperating system
Affected:all versions
Ir510 Wpan FirmwareOperating system
Affected:all versions

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:3.1/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. Identify device model and platform
    Use 'show version' command or check the physical device labeling to determine if the device is one of: Cisco Industrial Ethernet 2000 Series, Cisco IC3000, Cisco IE 4000, Cisco CGR 1000, Cisco IR510 WPAN, or Cisco iOS-based device with IOx capability
    Affected if Device is any of these models with IOx support
  2. Check firmware version
    Execute 'show version' or use the device's web interface/system info to retrieve the installed firmware version
    Affected if Version equals 1.6.0.0 or 1.8.0 on Cisco iOS, equals 15.2(6)e on Industrial Ethernet 2000 Series, or is any version on IC3000, IE4000, CGR1000, or IR510 WPAN
  3. Verify IOx is enabled
    Use 'show iox-service' command or check the IOx configuration via 'show running-config | include iox' to see if IOx is activated
    Affected if IOx service is enabled and running on the device
  4. Confirm IOx web interface is accessible
    Attempt to reach the IOx web interface via HTTPS on the management interface (typically port 443 or 8443) or verify listening status with 'show tcp brief' or similar network diagnostic
    Affected if The IOx HTTPS web server is exposed and accepting connections on the network

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 firmware update for the IOx application environment on affected platforms. If patching is not immediately possible, consider network-level filtering to restrict exposure of the IOx management interface.

Fix this in iOS Scoped from the published advisory
  • Consultation8.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,940
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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-2019-12656 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
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  • Version or environment caveats, and links to real fixes
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