CVE-2021-25136 – A buffer overflow vulnerability in the HPE Clou... (How to Fix)

Q: What is the severity of CVE-2021-25136?

CVE-2021-25136 has a CVSS score of 7.8 (HIGH). A buffer overflow vulnerability in the HPE Cloudline server BMC firmware allows local attackers to execute arbitrary code with elevated privileges. This affects administrators or users with physical or remote management access to the affected servers. The vulnerability resides in the SPX REST service's remote storage function.

📋 TL;DR

A buffer overflow vulnerability in the HPE Cloudline server BMC firmware allows local attackers to execute arbitrary code with elevated privileges. This affects administrators or users with physical or remote management access to the affected servers. The vulnerability resides in the SPX REST service's remote storage function.

💻 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 versions specified in HPE advisory

Operating Systems: Not applicable - BMC firmware vulnerability

Default Config Vulnerable: ⚠️ Yes

Notes: Requires local access to the BMC management interface (iLO).

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete compromise of the BMC, allowing persistent attacker control over server hardware, firmware modification, data exfiltration, and potential lateral movement to the host operating system.

🟠

Likely Case

BMC compromise leading to denial of service, configuration changes, or credential theft from the management interface.

🟢

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 management interface to trigger the vulnerable function.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Refer to HPE advisory for specific 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. Upload firmware via iLO web interface or command line. 3. Apply the update. 4. Reboot the BMC (server may need reboot).

🔧 Temporary Workarounds

Restrict BMC network access

all

Limit access to BMC management interfaces to trusted administrative networks only.

Configure firewall rules to restrict iLO/management port access
Use VLAN segmentation for management networks

Disable unused BMC services

all

Disable remote storage functions if not required.

Check iLO configuration for remote storage settings

🧯 If You Can't Patch

Isolate BMC management interfaces on dedicated, restricted networks
Implement strict access controls and multi-factor authentication for BMC access

🔍 How to Verify

Check if Vulnerable:

Check BMC firmware version via iLO web interface or SSH: show /map1/firmware1

Check Version:

ssh admin@bmc-ip 'show /map1/firmware1'

Verify Fix Applied:

Verify firmware version matches or exceeds patched version from HPE advisory

📡 Detection & Monitoring

Log Indicators:

Unusual authentication attempts to BMC
Multiple failed remote storage function calls
BMC firmware modification events

Network Indicators:

Unexpected connections to BMC management ports from unauthorized sources

SIEM Query:

source="ilo_logs" AND (event_id="authentication_failure" OR command="setsolvideoremotestorage")

📊 Metadata

CVE ID: CVE-2021-25136

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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