Ios XeOperating system · Cisco
CVE-2021-1431
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 vDaemon process of Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a device to reload, resulting a denial of service (DoS) condition. This vulnerability is due to insufficient handling of malformed packets. An attacker could exploit this vulnerability by sending crafted traffic to an affected device. A successful exploit could allow the attacker to cause the device to reload, 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 · high confidenceThis is a remote denial-of-service vulnerability in Cisco IOS XE SD-WAN Software's vDaemon process. The vulnerability exists because the vDaemon process does not properly handle malformed network packets, allowing an unauthenticated remote attacker to send crafted traffic that causes the affected device to reload.
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
= 3.15.1xbs= 3.15.2xbs= 16.11.1= 16.11.1a= 16.11.1b= 16.11.1c= 16.11.1s= 16.11.2= 16.12.1= 16.12.1a= 16.12.1c= 16.12.1sCVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify the IOS XE versionRun 'show version' on the device CLI and locate the version string (for example, 16.11.1, 16.12.1s, 3.15.1xbs)Affected if The displayed version matches any of these: 3.15.1xbs, 3.15.2xbs, 16.11.1, 16.11.1a, 16.11.1b, 16.11.1c, 16.11.1s, 16.11.2, 16.12.1, 16.12.1a, 16.12.1c, 16.12.1s
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Confirm the device runs IOS XE SD-WANRun 'show version' and verify the software description mentions 'IOS XE' and look for SD-WAN in the feature setAffected if The software is Cisco IOS XE with SD-WAN capability
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Verify the vDaemon process is runningRun 'show process cpu | include vDaemon' or 'show process | include vDaemon' to check if the vDaemon process is activeAffected if The vDaemon process is present and running on the device
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Check if SD-WAN interfaces are activeRun 'show sdwan interface' or 'show sdwan brief' to confirm SD-WAN tunnels and interfaces are configured and upAffected if SD-WAN interfaces or tunnels are active and passing traffic
You are affected if your device runs any of the listed IOS XE versions AND has SD-WAN enabled with the vDaemon process running, as the vulnerability can be triggered by malformed packets sent to the vDaemon interface.
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 relevant Cisco security patch for Cisco IOS XE SD-WAN Software. If a patch is unavailable, mitigate by restricting network access to the vDaemon interface and implementing ingress traffic filtering to block malformed packets.
Fix this in Ios Xe
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1431 — 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-2021-1431 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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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.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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