iOSOperating system · Cisco
CVE-2020-3426
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 · uneditedA vulnerability in the implementation of the Low Power, Wide Area (LPWA) subsystem of Cisco IOS Software for Cisco 800 Series Industrial Integrated Services Routers (Industrial ISRs) and Cisco 1000 Series Connected Grid Routers (CGR1000) could allow an unauthenticated, remote attacker to gain unauthorized read access to sensitive data or cause a denial of service (DoS) condition. The vulnerability is due to a lack of input and validation checking mechanisms for virtual-LPWA (VLPWA) protocol modem messages. An attacker could exploit this vulnerability by supplying crafted packets to an affected device. A successful exploit could allow the attacker to gain unauthorized read access to sensitive data or cause the VLPWA interface of the affected device to shut down, resulting in 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 · high confidenceA lack of input validation in the virtual-LPWA (VLPWA) protocol modem message handling within Cisco IOS Software for Industrial ISRs and Connected Grid Routers allows unauthenticated, remote attackers to send crafted packets that either enable unauthorized read access to sensitive data or cause the VLPWA interface to shut down, resulting in denial of service.
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
all versionsCVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify device type and modelConfirm the device is a Cisco Industrial ISR or Connected Grid Router by running 'show version' or 'show inventory' commands and checking the model number and descriptionAffected if Device is an Industrial ISR or Connected Grid Router model running Cisco IOS
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Verify Cisco IOS is runningExecute 'show version' to confirm the operating system is Cisco IOS rather than IOS-XE or other variantsAffected if Device runs Cisco IOS (not IOS-XE or NX-OS)
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Determine if VLPWA interface is configuredRun 'show ip interface brief' or 'show interfaces' to look for VLPWA-related interfaces. Use 'show running-config | include vlpwa' to search for VLPWA configuration in the running configAffected if A VLPWA virtual interface is present and active on the device
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Check for VLPWA modem messaging activityUse 'show vlpwa' or 'show vlpwa interface' commands (if available) to examine VLPWA protocol status and modem message handling statisticsAffected if VLPWA interface shows active modem communication and is reachable on the network
The device is affected if it is an Industrial ISR or Connected Grid Router running Cisco IOS with a configured and active VLPWA interface accessible to unauthenticated network attackers.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the vendor-supplied Cisco IOS software update for this vulnerability. As an interim measure, restrict network access to the VLPWA interface and implement network segmentation to limit exposure to unauthenticated attackers.
Fix this in iOS
Scoped from the published advisory
- Consultation8.0 h
- Implementation12.0 h
- Testing16.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,160.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3426 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-3426 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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