Security readout for executives and security teams
Plain-English summary
CVE-2019-1951 lets a remote unauthenticated attacker bypass Cisco SD-WAN L3/L4 traffic filters and inject an arbitrary packet into the network. Business risk is loss of expected segmentation or policy enforcement, not system takeover based on the provided evidence.
Executive priority
Treat as a moderate priority if Cisco SD-WAN filters protect sensitive segments or branch traffic paths. It should not outrank critical remote code execution issues, but it can weaken network policy assumptions and deserves timely vendor-guided remediation.
Technical view
Cisco describes improper traffic filtering conditions in Cisco SD-WAN Solution. A crafted TCP packet with specific characteristics can bypass packet filtering features. The CVSS v3.0 score is 5.8, with network attack vector, low complexity, no privileges, no user interaction, changed scope, and low integrity impact.
Likely exposure
Exposure is most relevant where Cisco SD-WAN Solution is deployed and its L3/L4 filters are relied on for segmentation, access control, or traffic policy enforcement. The source bundle does not specify affected releases or CPEs.
Exploitation context
The bundle does not show CISA KEV listing or confirmed active exploitation. It states exploitation is remote and unauthenticated, but only through specially crafted TCP traffic. No exploit maturity, public exploit availability, or real-world incident evidence is provided.
Researcher notes
The available evidence is concise: product family, bypass class, CWE-20, CVSS, and vendor advisory link. Affected versions and concrete fixes are not included in the source bundle, so verification should hinge on Cisco’s advisory rather than assumptions.
Mitigation direction
- Review the Cisco advisory for affected releases and fixed software guidance.
- Prioritize Cisco SD-WAN devices enforcing L3/L4 segmentation or access policies.
- Apply vendor-recommended updates or mitigations where Cisco identifies affected deployments.
- Use compensating controls where critical policy enforcement depends on affected filtering.
- Monitor for unexpected traffic paths crossing SD-WAN filter boundaries.
Validation and detection
- Inventory Cisco SD-WAN Solution deployments and software versions.
- Identify sites relying on SD-WAN L3/L4 filters for security enforcement.
- Compare deployed versions against the Cisco advisory.
- Review firewall and SD-WAN policy logs for unexpected allowed traffic.
- Confirm post-remediation filtering behavior with approved defensive tests.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2019-1951 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
5.8MediumVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- 20190807 Cisco SD-WAN Solution Packet Filtering Bypass VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.