CVE-2021-38515 – This vulnerability affects specific NETGEAR rou... (How to Fix)

Q: What is the severity of CVE-2021-38515?

CVE-2021-38515 has a CVSS score of 7.4 (HIGH). This vulnerability affects specific NETGEAR router models, allowing attackers to cause denial of service by crashing the device. Affected users include those running vulnerable firmware versions on R6400v2, R6700v3, R7900, and R8000 routers.

📋 TL;DR

This vulnerability affects specific NETGEAR router models, allowing attackers to cause denial of service by crashing the device. Affected users include those running vulnerable firmware versions on R6400v2, R6700v3, R7900, and R8000 routers.

💻 Affected Systems

Products:

NETGEAR R6400v2
NETGEAR R6700v3
NETGEAR R7900
NETGEAR R8000

Versions: R6400v2 before 1.0.4.98, R6700v3 before 1.0.4.98, R7900 before 1.0.3.18, R8000 before 1.0.4.46

Operating Systems: Router firmware

Default Config Vulnerable: ⚠️ Yes

Notes: All devices running affected firmware versions are vulnerable regardless of configuration.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Router becomes completely unresponsive, requiring physical power cycle and potentially causing extended network downtime.

🟠

Likely Case

Router crashes and reboots, causing temporary network disruption until device restarts.

🟢

If Mitigated

No impact if patched firmware is installed.

🌐 Internet-Facing: HIGH - Routers are directly internet-facing devices that can be targeted remotely.

🏢 Internal Only: LOW - This primarily affects external attack surface, though internal attackers could also exploit.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Based on CVSS score and DoS nature, exploitation likely requires minimal technical skill.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: R6400v2: 1.0.4.98+, R6700v3: 1.0.4.98+, R7900: 1.0.3.18+, R8000: 1.0.4.46+

Vendor Advisory: https://kb.netgear.com/000063768/Security-Advisory-for-Denial-of-Service-on-Some-Routers-PSV-2019-0082

Restart Required: Yes

Instructions:

1. Log into router admin interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates or manually download latest firmware from NETGEAR support site. 4. Upload and install firmware update. 5. Router will reboot automatically.

🔧 Temporary Workarounds

Disable remote management

all

Prevents external attackers from accessing router management interface.

Enable firewall rules

all

Restrict incoming connections to router management interface.

🧯 If You Can't Patch

Replace affected router with updated model or different vendor
Place router behind additional firewall or security appliance

🔍 How to Verify

Check if Vulnerable:

Check router firmware version in admin interface under Advanced > Administration > Firmware Update

Check Version:

No CLI command - check via web interface at http://routerlogin.net or router IP

Verify Fix Applied:

Confirm firmware version matches or exceeds patched versions listed in advisory

📡 Detection & Monitoring

Log Indicators:

Router crash logs
Unexpected reboots
High CPU/memory usage before crash

Network Indicators:

Sudden loss of connectivity
Router becoming unresponsive to ping

SIEM Query:

Device logs showing router reboot events or connectivity loss patterns

📊 Metadata

CVE ID: CVE-2021-38515

CVSS v3 Score: 7.4 (HIGH)

CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Published: August 11, 2021

Last Updated: November 21, 2024

🔗 References

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