CVE-2021-25126 – A buffer overflow vulnerability in the Baseboar... (How to Fix)

Q: What is the severity of CVE-2021-25126?

CVE-2021-25126 has a CVSS score of 7.8 (HIGH). A buffer overflow vulnerability in the Baseboard Management Controller (BMC) firmware of specific HPE Cloudline servers allows local attackers to execute arbitrary code. This affects administrators or users with local access to the BMC interface. Successful exploitation could lead to complete compromise of the BMC.

📋 TL;DR

A buffer overflow vulnerability in the Baseboard Management Controller (BMC) firmware of specific HPE Cloudline servers allows local attackers to execute arbitrary code. This affects administrators or users with local access to the BMC interface. Successful exploitation could lead to complete compromise of the BMC.

💻 Affected Systems

Products:

HPE Cloudline CL5800 Gen9 Server
HPE Cloudline CL5200 Gen9 Server
HPE Cloudline CL4100 Gen10 Server
HPE Cloudline CL3100 Gen10 Server
HPE Cloudline CL5800 Gen10 Server

Versions: BMC firmware versions prior to the fixed versions specified in HPE advisory

Operating Systems: Not applicable - BMC firmware vulnerability

Default Config Vulnerable: ⚠️ Yes

Notes: Requires local access to the BMC REST service interface. The vulnerability is in the downloadkvmjnlp_func function of spx_restservice.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete BMC compromise allowing persistent attacker foothold, credential theft, and potential lateral movement to the host operating system.

🟠

Likely Case

Local privilege escalation on the BMC leading to unauthorized administrative access and potential denial of service.

🟢

If Mitigated

Limited impact if proper network segmentation and access controls prevent unauthorized BMC access.

🌐 Internet-Facing: MEDIUM - Only if BMC interfaces are exposed to the internet without proper firewalling.

🏢 Internal Only: HIGH - Attackers with internal network access could exploit this to gain BMC control.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access to the BMC interface. Buffer overflow exploitation typically requires some technical skill but is well-understood.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Refer to HPE advisory HPSBHF04073 for specific fixed firmware versions for each server model

Vendor Advisory: https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf04073en_us

Restart Required: Yes

Instructions:

1. Download the updated BMC firmware from HPE Support Portal. 2. Follow HPE's firmware update procedures for your specific server model. 3. Apply the firmware update through the BMC web interface or using HPE tools. 4. Reboot the BMC to complete the update.

🔧 Temporary Workarounds

Restrict BMC Network Access

all

Limit access to BMC management interfaces to authorized administrative networks only

Configure firewall rules to restrict access to BMC IP addresses on ports 80/443/623/664

Disable Unnecessary BMC Services

all

Disable the REST service if not required for operations

Check HPE documentation for disabling specific BMC services through web interface or CLI

🧯 If You Can't Patch

Implement strict network segmentation to isolate BMC interfaces from general network traffic
Enable BMC audit logging and monitor for suspicious access attempts

🔍 How to Verify

Check if Vulnerable:

Check BMC firmware version through web interface (System Information → Firmware) or using ipmitool: ipmitool mc info

Check Version:

ipmitool mc info | grep 'Firmware Revision'

Verify Fix Applied:

Confirm BMC firmware version matches or exceeds the patched version listed in HPE advisory HPSBHF04073

📡 Detection & Monitoring

Log Indicators:

Unusual BMC authentication attempts
Multiple failed REST service requests
BMC service crashes or restarts

Network Indicators:

Unusual traffic patterns to BMC REST service endpoints
Exploit-like payloads sent to BMC management ports

SIEM Query:

source="BMC" AND (event_type="authentication_failure" OR event_type="service_crash")

📊 Metadata

CVE ID: CVE-2021-25126

CVSS v3 Score: 7.8 (HIGH)

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

CWE: CWE-120

Published: January 29, 2021

Last Updated: November 21, 2024

🔗 References

https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf04073en_us Vendor Advisory
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf04073en_us Vendor Advisory

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