Security readout for executives and security teams
Plain-English summary
This issue affects several older NETGEAR router models and could let an already authenticated user trigger a stack-based buffer overflow. The rated impact is serious for confidentiality, integrity, and availability, but the attack requires high privileges and adjacent-network access, reducing broad internet-scale urgency.
Executive priority
Treat as a targeted network-device remediation item, not an emergency mass-exploitation event based on available evidence. Prioritize internet-edge and business-critical locations first, especially where router administration is weakly controlled.
Technical view
CVE-2018-21135 is a post-authentication stack-based buffer overflow in listed NETGEAR routers. The CVSS 3.0 vector is AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H, scoring 6.8. Fixed-version thresholds are provided for R6700, R7500, R7800, R8900, R9000, WNDR3700v4, WNDR4300v1/v2, WNDR4500v3, and WNR2000v5-R2000.
Likely exposure
Exposure is limited to the named NETGEAR models running firmware below the listed fixed versions. Organizations are most likely exposed through branch, small-office, lab, or unmanaged network routers that have not received firmware maintenance.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. The CVSS vector indicates exploitation requires adjacent-network access and high privileges, with no user interaction. Evidence is insufficient to claim public weaponization or unauthenticated remote exploitation.
Researcher notes
The CNA description provides product/version thresholds but no CWE mapping, exploit narrative, or detailed vulnerable component. Analysis should stay scoped to authenticated adjacent-network exposure and vendor firmware status unless additional primary sources are obtained.
Mitigation direction
- Inventory NETGEAR routers and match models against the advisory list.
- Compare firmware versions with the fixed-version thresholds in the CVE description.
- Update affected routers to vendor-recommended fixed firmware where available.
- Restrict router administration to trusted accounts and management networks.
- Replace unsupported devices that cannot be updated safely.
Validation and detection
- Confirm each device model and exact firmware version from administration records.
- Document whether firmware is below the fixed threshold for that model.
- Review NETGEAR advisory guidance before applying changes.
- Check for unexpected administrative accounts or recent configuration changes.
- Retest inventory after updates to confirm fixed firmware is installed.
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.
CVE-2018-21135 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
- 6.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AC:L/AV:A/A:H/C:H/I:H/PR:H/S:U/UI: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/AC:L/AV:A/A:H/C:H/I:H/PR:H/S:U/UI:N0.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
6.8MediumVector: CVSS:3.0/AC:L/AV:A/A:H/C:H/I:H/PR:H/S:U/UI:N
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.netgear.com/000060225/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-PSV-2017-3165CVE reference · x_refsource_CONFIRM
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.