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CVE-2026-16864 is a critical 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 network input, where insufficient bounds checking on data copied into a fixed-size stack buffer allows an attacker to overwrite adjacent memory. By sending a specially crafted request to a vulnerable service, a remote, unauthenticated attacker can trigger this overflow and overwrite the return address on the stack. This hijacks the execution flow, enabling arbitrary code execution with the privileges of the affected process—typically root or system-level authority.
The vulnerability is classified under CWE-787: Out-of-bounds Write. It is remotely exploitable over a network without authentication or user interaction, making it particularly dangerous in production environments. The CVSS v3.1 base score is 9.8 (Critical), with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H—indicating full compromise of confidentiality, integrity, and availability. The CVSS v2 base score is 10.0. The flaw affects all AIX 7.2 and 7.3 releases prior to the fixed service packs, and all VIOS 4.1 releases prior to the fixed fix packs. Patches were made available starting August 14, 2026, and IBM has published cumulative service packs and fix packs that address this vulnerability along with other security issues.
DailyCVE Form:
Platform: IBM AIX / VIOS
Version: 7.2, 7.3, 4.1
Vulnerability: Stack Buffer Overflow
Severity: Critical (9.8)
Date: August 19, 2026
Prediction: Patch already available
What Undercode Say:
Check AIX version oslevel -s Check VIOS version ioslevel Verify if vulnerable (example - check installed fileset levels) lslpp -L bos.rte Download fix from IBM Fix Central https://www.ibm.com/support/fixcentral Apply AIX Service Pack (example for 7.3 TL04 SP2) installp -d /path/to/SP -acgXd . all Apply VIOS Fix Pack (example for 4.1.2.20) updateios -install /path/to/FP
Exploit: (Educational Purposes!)
A remote attacker crafts a malicious network packet containing payload data that exceeds the expected length of a stack-allocated buffer in a listening service. The oversized input overwrites the saved return address on the stack. When the vulnerable function returns, the CPU loads the overwritten address, redirecting execution to attacker-controlled shellcode injected within the payload. This grants the attacker a remote shell with root privileges.
Protection:
- Apply the fixed AIX Service Packs: 7.3 TL04 SP2, 7.3 TL03 SP3, 7.3 TL02 SP5, or 7.2 TL05 SP13
- Apply the fixed VIOS Fix Packs: 4.1.2.20, 4.1.1.30, or 4.1.0.50
- Restrict network access to AIX/VIOS administrative services using firewalls
- Deploy intrusion detection/prevention systems to monitor for anomalous traffic
- Use AIX Live Update to apply patches without reboot where possible
Impact:
Successful exploitation allows an unauthenticated remote attacker to execute arbitrary code with system-level privileges, leading to complete system compromise, data theft, malware installation, and use of the compromised host as a pivot point for lateral movement within the network.
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Sources:
Reported By: nvd.nist.gov
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