Sd Wan FirmwareOperating system · Cisco
CVE-2019-1951
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 packet filtering features of Cisco SD-WAN Solution could allow an unauthenticated, remote attacker to bypass L3 and L4 traffic filters. The vulnerability is due to improper traffic filtering conditions on an affected device. An attacker could exploit this vulnerability by crafting a malicious TCP packet with specific characteristics and sending it to a target device. A successful exploit could allow the attacker to bypass the L3 and L4 traffic filters and inject an arbitrary packet in the network.
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 confidenceThis is a filter bypass vulnerability in Cisco SD-WAN's packet filtering functionality. Improper traffic filtering conditions allow specially crafted TCP packets to bypass L3 and L4 layer filters, potentially enabling attackers to inject arbitrary packets into the network.
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
Sd Wan FirmwareOperating system
<= 19.1.0CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
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 SD-WAN firmware versionAccess the vManage web interface or CLI and retrieve the current firmware version. In CLI, this is typically shown via 'show version' or 'show software' commands. In vManage, check System > Settings > Software Updates or the Dashboard for the current version.Affected if The installed version is 19.1.0 or any earlier version
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Verify packet filtering is enabledConfirm whether L3/L4 packet filtering, firewall policies, or ACLs are configured on the SD-WAN edge devices. Check the security policy configuration in vManage under Configuration > Security or examine edge device configs via CLI with 'show running-config | include filter|firewall|acl'.Affected if Filtering features are actively applied to traffic flows
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Review L3/L4 filter rulesInspect the configured L3 and L4 filter rules, ACLs, or firewall policies in the SD-WAN configuration. Look for TCP-based rules that might be subject to the bypass. In vManage, navigate to Configuration > Security > Firewall or access device configs via CLI with 'show running-config | section firewall'.Affected if TCP-based L3/L4 filters are present in the configuration
If the SD-WAN firmware is version 19.1.0 or earlier AND L3/L4 packet filtering is enabled with TCP rules configured, the environment is likely affected by this vulnerability.
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 Cisco's available security patches for this vulnerability and review existing L3/L4 filter configurations to ensure they are functioning as intended.
Fix this in Sd Wan Firmware
Scoped from the published advisory
- Consultation6.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,816.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-1951 — 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-2019-1951 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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