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iOSOperating system · Cisco

CVE-2020-3409

HIGH · 7.4 CVSS v3.1 Published 2020-09-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
79/100
Remediation priority · High
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 PROFINET feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause an affected device to crash and reload, resulting in a denial of service (DoS) condition on the device. The vulnerability is due to insufficient processing logic for crafted PROFINET packets that are sent to an affected device. An attacker could exploit this vulnerability by sending crafted PROFINET packets to an affected device for processing. A successful exploit could allow the attacker to cause the device to crash and reload, resulting in a DoS condition on the device.

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 denial of service vulnerability exists in the PROFINET feature of Cisco IOS Software and Cisco IOS XE Software. The vulnerability stems from insufficient processing logic that fails to properly handle crafted PROFINET packets sent to an affected device. An adjacent, unauthenticated attacker can exploit this by sending specially crafted PROFINET packets, causing the device to crash and reload repeatedly.

MitigationApply the appropriate Cisco security updates/patches for this vulnerability to affected devices. Since the attack requires adjacent network access, network segmentation may provide temporary risk reduction while patching is planned.

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:= 15.2\(7\)e= 16.11.1a
Ios XeOperating system
Affected:= 15.2\(7\)e= 16.11.1a

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 installed software product and version
    Run 'show version' on the device CLI and look for either 'IOS Software' or 'IOS XE Software' in the output, along with the release number (e.g., 15.2(7)e or 16.11.1a)
    Affected if The device runs Cisco IOS or IOS XE and the version matches 15.2(7)e or 16.11.1a
  2. Confirm the device has PROFINET configured
    Run 'show running-config | include profinet' or check the device configuration for any 'profinet' related commands such as 'profinet enable' or PROFINET VLAN configurations
    Affected if PROFINET feature or protocol is enabled in the device configuration
  3. Check for PROFINET-related interfaces
    Run 'show interfaces' or 'show ip interface brief' and look for any interfaces that may have PROFINET VLAN or discovery enabled
    Affected if Any interface is configured for PROFINET traffic or VLANs
  4. Verify if the device has recently experienced reload events
    Run 'show reload' to check for scheduled reloads, and review 'show logging' or 'show tech-support' for evidence of unexpected reloads or crashes that may indicate exploitation
    Affected if Device has reloaded unexpectedly or shows crash history without clear cause

A device is affected if it runs Cisco IOS or IOS XE version 15.2(7)e or 16.11.1a AND has PROFINET feature enabled or configured, making it vulnerable to crafted PROFINET packet attacks causing repeated crashes.

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 security updates/patches for this vulnerability to affected devices. Since the attack requires adjacent network access, network segmentation may provide temporary risk reduction while patching is planned.

Fix this in iOS 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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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-2020-3409 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data