HOMEVULNERABILITIESCVE-2021-27239
HIGH

CVE-2021-27239

CWE-121Published: March 29, 2021· Updated: Jun 17, 2026

8.8
CVSS v3.1

Official Description

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400 and R6700 firmware version 1.0.4.98 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the upnpd service, which listens on UDP port 1900 by default. A crafted MX header field in an SSDP message can trigger an overflow of a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-11851.

NVD Source

Technical Analysis

CVE-2021-27239 requires adjacent network access, limiting remote exploitation but still posing risk in shared or local network environments.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorAdjacent
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

netgear70 product(s)
d6220 firmwared6220d6400 firmwared6400d7000 firmwared7000d8500 firmwared8500dc112a firmwaredc112aex7000 firmwareex7000+58
Source: NVD CPE · 71 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Routers-PSV-2020-0432
ADVISORYhttps://www.zerodayinitiative.com/advisories/ZDI-21-206/
ADVISORYhttps://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Routers-PSV-2020-0432
ADVISORYhttps://www.zerodayinitiative.com/advisories/ZDI-21-206/

All References (4)

→
https://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Routers-PSV-2020-0432Vendor Advisory
→
https://www.zerodayinitiative.com/advisories/ZDI-21-206/Third Party Advisory · VDB Entry
→
https://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Routers-PSV-2020-0432Vendor Advisory
→
https://www.zerodayinitiative.com/advisories/ZDI-21-206/Third Party Advisory · VDB Entry

Quick Facts

CVE IDCVE-2021-27239
CVSS Score8.8 / 10
SeverityHIGH
WeaknessCWE-121
CISA KEVNo
Affected1 vendor(s)
PublishedMar 29, 2021

Related CVEs (CWE-121)

CVE-2014-9190
10.0
CVE-2020-14498
10.0
CVE-2026-12846
10.0
CVE-2026-12847
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CVE-2014-0787
10.0
CVE-2026-12848
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-27239 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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