CVE-2021-25138 – A local buffer overflow vulnerability in the Ba... (How to Fix)

Q: What is the severity of CVE-2021-25138?

CVE-2021-25138 has a CVSS score of 7.8 (HIGH). A local buffer overflow vulnerability in the Baseboard Management Controller (BMC) firmware of specific HPE Cloudline servers allows authenticated attackers to execute arbitrary code with elevated privileges. This affects administrators or users with BMC access to HPE Cloudline CL5800 Gen9, CL5200 Gen9, CL4100 Gen10, CL3100 Gen10, and CL5800 Gen10 servers.

📋 TL;DR

A local buffer overflow vulnerability in the Baseboard Management Controller (BMC) firmware of specific HPE Cloudline servers allows authenticated attackers to execute arbitrary code with elevated privileges. This affects administrators or users with BMC access to HPE Cloudline CL5800 Gen9, CL5200 Gen9, CL4100 Gen10, CL3100 Gen10, and CL5800 Gen10 servers.

💻 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 patched version

Operating Systems: Not applicable - BMC firmware vulnerability

Default Config Vulnerable: ⚠️ Yes

Notes: Requires authenticated access to the BMC interface. The vulnerability is in the spx_restservice uploadsshkey function.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full BMC compromise leading to persistent server control, credential theft, firmware modification, and potential lateral movement to other systems.

🟠

Likely Case

BMC takeover allowing unauthorized server management, monitoring data access, and potential denial of service.

🟢

If Mitigated

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

🌐 Internet-Facing: MEDIUM

🏢 Internal Only: HIGH

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires authenticated access to the BMC interface. Buffer overflow exploitation typically requires some technical skill.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Refer to HPE advisory for specific patched firmware versions

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. Access the BMC web interface. 3. Navigate to firmware update section. 4. Upload and apply the firmware update. 5. Reboot the BMC as required.

🔧 Temporary Workarounds

Restrict BMC Network Access

all

Limit access to BMC interfaces to only authorized management networks and IP addresses.

Disable Unnecessary BMC Services

all

Disable the REST service or SSH key upload functionality if not required.

🧯 If You Can't Patch

Isolate BMC management interfaces on separate VLAN with strict firewall rules
Implement multi-factor authentication and strong credential policies for BMC access

🔍 How to Verify

Check if Vulnerable:

Check BMC firmware version via web interface or IPMI commands and compare against HPE advisory

Check Version:

ipmitool mc info | grep 'Firmware Revision' or check via BMC web interface

Verify Fix Applied:

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

📡 Detection & Monitoring

Log Indicators:

Multiple failed authentication attempts to BMC
Unusual SSH key upload activities
BMC firmware modification logs

Network Indicators:

Unusual traffic to BMC IP addresses from unauthorized sources
Exploit pattern detection in BMC traffic

SIEM Query:

source="BMC" AND (event="authentication_failure" OR event="firmware_update" OR event="ssh_key_upload")

📊 Metadata

CVE ID: CVE-2021-25138

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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