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CVE Record

CVE-2021-40847: The update process of the Circle Parental Control Service on various NETGEAR routers allows remote attacker...

The update process of the Circle Parental Control Service on various NETGEAR routers allows remote attackers to achieve remote code execution as root via a MitM attack. While the parental controls themselves are not enabled by default on the routers, the Circle update daemon, circled, is enabled by default. This daemon connects to Circle and NETGEAR to obtain version information and updates to the circled daemon and its filtering database. However, database updates from NETGEAR are unsigned and downloaded via cleartext HTTP. As such, an attacker with the ability to perform a MitM attack on the device can respond to circled update requests with a crafted, compressed database file, the extraction of which gives the attacker the ability to overwrite executable files with attacker-controlled code. This affects R6400v2 1.0.4.106, R6700 1.0.2.16, R6700v3 1.0.4.106, R6900 1.0.2.16, R6900P 1.3.2.134, R7000 1.0.11.123, R7000P 1.3.2.134, R7850 1.0.5.68, R7900 1.0.4.38, R8000 1.0.4.68, and RS400 1.5.0.68.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Some NETGEAR routers run the Circle update daemon by default. The supplied sources say it fetched unsigned database updates over cleartext HTTP, so an attacker able to intercept that traffic could cause root-level code execution. Parental controls did not need to be enabled.

Executive priority

Treat this as high priority for exposed or business-critical NETGEAR routers, especially where traffic interception is plausible. Root execution on a router can compromise network trust, but the supplied evidence does not show active exploitation.

Technical view

The issue is in circled, the Circle Parental Control Service update daemon. Database updates from NETGEAR were unsigned and downloaded over HTTP. A man-in-the-middle attacker could provide a crafted compressed database whose extraction overwrote executable files with attacker-controlled code, resulting in remote code execution as root.

Likely exposure

Exposure is limited to the listed NETGEAR router models and firmware versions where circled is enabled by default. The bundle names R6400v2, R6700, R6700v3, R6900, R6900P, R7000, R7000P, R7850, R7900, R8000, and RS400 versions.

Exploitation context

The supplied evidence requires an attacker to perform a man-in-the-middle attack against the router’s update traffic. The CVE is not marked KEV in the bundle, and no supplied source states active exploitation.

Researcher notes

The key exposure condition is not parental-control use; it is the default-running circled daemon and insecure update path. Source details are strong on root RCE mechanics, but the bundle does not include CVSS, CWE, fixed versions, or exploitation-in-the-wild evidence.

Mitigation direction

  • Review NETGEAR advisory PSV-2021-0204 for affected models and fixed firmware guidance.
  • Update affected routers using only vendor-provided firmware and trusted administration paths.
  • If vendor guidance allows, disable or restrict the Circle update service until patched.
  • Retire affected routers that cannot be updated to a vendor-supported fixed release.

Validation and detection

  • Inventory router model and firmware version against the affected list in the CVE description.
  • Confirm whether circled or Circle update functionality is present and enabled.
  • Verify firmware update status against NETGEAR advisory PSV-2021-0204.
  • Check monitoring for unexpected router configuration, firmware, or executable changes.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Execution behavior lookup

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Database behavior lookup

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CVE-2021-40847 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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