High-Severity RCE Flaw Disclosed in Several Netgear Router Models

Sep 21, 2021

Networking equipment company Netgear has released patches to
remediate a high-severity remote code execution vulnerability
affecting multiple routers that could be exploited by remote
attackers to take control of an affected system.

Traced as CVE-2021-40847 ^[1]
(CVSS score: 8.1), the security weakness impacts the following
models –

R6400v2 (fixed in firmware version 1.0.4.120)
R6700 (fixed in firmware version 1.0.2.26)
R6700v3 (fixed in firmware version 1.0.4.120)
R6900 (fixed in firmware version 1.0.2.26)
R6900P (fixed in firmware version 3.3.142_HOTFIX)
R7000 (fixed in firmware version 1.0.11.128)
R7000P (fixed in firmware version 1.3.3.142_HOTFIX)
R7850 (fixed in firmware version 1.0.5.76)
R7900 (fixed in firmware version 1.0.4.46)
R8000 (fixed in firmware version 1.0.4.76)
RS400 (fixed in firmware version 1.5.1.80)

According to GRIMM security researcher Adam Nichols, the
vulnerability resides within Circle ^[2], a third-party component
included in the firmware that offers parental control features,
with the Circle update daemon enabled to run by default even if the
router hasn’t been configured to limit daily internet time for
websites and apps. This results in a scenario that could permit bad
actors with network access to gain remote code execution (RCE) as
root via a Man-in-the-Middle (MitM) attack.

This is made possible owing to the manner in which the update
daemon (called “circled”) connects to Circle and Netgear to fetch
updates to the filtering database — which are both unsigned and
downloaded using HTTP — thereby making it possible for an
interloper to stage a MitM attack and respond to the update request
with a specially-crafted compressed database file, extracting which
gives the attacker the ability to overwrite executable binaries
with malicious code.

“Since this code is run as root on the affected routers,
exploiting it to obtain RCE is just as damaging as a RCE
vulnerability found in the core Netgear firmware,” Nichols said ^[3]. “This particular
vulnerability once again demonstrates the importance of attack
surface reduction.”

The disclosure comes weeks after Google security engineer
Gynvael Coldwind revealed details of three severe security
vulnerabilities dubbed Demon’s Cries, Draconian Fear ^[4], and Seventh Inferno ^[5], impacting over a dozen
of its smart switches, allowing threat actors to bypass
authentication and gain full control of vulnerable devices.

References

^{^}
CVE-2021-40847
(kb.netgear.com)
^{^}
Circle
(www.netgear.com)
^{^}
said
(blog.grimm-co.com)
^{^}
Demon’s
Cries, Draconian Fear (thehackernews.com)
^{^}
Seventh
Inferno (thehackernews.com)

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OWASP TOP !0

Injection. Injection flaws, such as SQL, NoSQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization. Broken Authentication. Application functions related to authentication and session management are often implemented incorrectly, allowing attackers to compromise passwords, keys, or session tokens, or to exploit other implementation flaws to assume other users’ identities temporarily or permanently. Sensitive Data Exposure. Many web applications and APIs do not properly protect sensitive data, such as financial, healthcare, and PII. Attackers may steal or modify such weakly protected data to conduct credit card fraud, identity theft, or other crimes. Sensitive data may be compromised without extra protection, such as encryption at rest or in transit, and requires special precautions when exchanged with the browser. XML External Entities (XXE). Many older or poorly configured XML processors evaluate external entity references within XML documents. External entities can be used to disclose internal files using the file URI handler, internal file shares, internal port scanning, remote code execution, and denial of service attacks. Broken Access Control. Restrictions on what authenticated users are allowed to do are often not properly enforced. Attackers can exploit these flaws to access unauthorized functionality and/or data, such as access other users’ accounts, view sensitive files, modify other users’ data, change access rights, etc. Security Misconfiguration. Security misconfiguration is the most commonly seen issue. This is commonly a result of insecure default configurations, incomplete or ad hoc configurations, open cloud storage, misconfigured HTTP headers, and verbose error messages containing sensitive information. Not only must all operating systems, frameworks, libraries, and applications be securely configured, but they must be patched/upgraded in a timely fashion. Cross-Site Scripting XSS. XSS flaws occur whenever an application includes untrusted data in a new web page without proper validation or escaping, or updates an existing web page with user-supplied data using a browser API that can create HTML or JavaScript. XSS allows attackers to execute scripts in the victim’s browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites. Insecure Deserialization. Insecure deserialization often leads to remote code execution. Even if deserialization flaws do not result in remote code execution, they can be used to perform attacks, including replay attacks, injection attacks, and privilege escalation attacks. Using Components with Known Vulnerabilities. Components, such as libraries, frameworks, and other software modules, run with the same privileges as the application. If a vulnerable component is exploited, such an attack can facilitate serious data loss or server takeover. Applications and APIs using components with known vulnerabilities may undermine application defenses and enable various attacks and impacts. Insufficient Logging & Monitoring. Insufficient logging and monitoring, coupled with missing or ineffective integration with incident response, allows attackers to further attack systems, maintain persistence, pivot to more systems, and tamper, extract, or destroy data. Most breach studies show time to detect a breach is over 200 days, typically detected by external parties rather than internal processes or monitoring.

High-Severity RCE Flaw Disclosed in Several Netgear Router Models

References

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