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CVE-2026-17423 is a critical vulnerability affecting IBM AIX versions 7.2 and 7.3, as well as IBM PowerVM VIOS version 4.1. The flaw resides in an out-of-bounds read condition, which occurs when software reads data beyond the intended boundaries of a memory buffer. This type of weakness is classified under CWE-125.
The vulnerability can be triggered remotely, allowing an attacker to access sensitive information from adjacent memory locations, and in many cases, cause a system crash or denial of service. According to the CVSS metrics provided by NIST, the vulnerability has a base score of 9.1 (Critical) with the vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H. This indicates a network-accessible attack with low complexity, requiring no privileges or user interaction, resulting in high confidentiality and availability impacts.
Interestingly, IBM Corporation’s own assessment gives it a score of 7.7 (High) with a slightly different vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H. The distinction lies in the Attack Vector—NIST considers it remotely exploitable (AV:N), while IBM classifies it as locally exploitable (AV:L). Regardless, the potential for information disclosure and service disruption is severe.
The vulnerability arises from improper validation of input data or index values, leading to pointer arithmetic that references memory outside the allocated buffer. When the code reads a variable amount of data and assumes a sentinel (like a NULL terminator) exists to stop the read, the sentinel may not be present in out-of-bounds memory. This causes excessive data to be read, resulting in a segmentation fault or leakage of sensitive kernel or process memory.
IBM has acknowledged the issue and released cumulative security updates via Service Packs (SPs) for AIX and Fix Packs (FPs) for VIOS. The fixes are available through IBM Fix Central. Affected versions include AIX 7.2.5 through 7.2.5.212, 7.3.2 through 7.3.2.5, 7.3.3 through 7.3.3.2, 7.3.4 through 7.3.4.1, and VIOS 4.1.0 up to (excluding) 4.1.0.50, 4.1.1.0 up to (excluding) 4.1.1.30, and 4.1.2.0 up to (excluding) 4.1.2.20.
DailyCVE Form:
Platform: IBM AIX/PowerVM VIOS
Version: 7.2, 7.3, 4.1
Vulnerability: Out-of-bounds Read
Severity: Critical (9.1 CVSS)
date: 08/20/2026
Prediction: Patches available since 08/14/2026
What Undercode Say:
Check AIX version oslevel -s Check VIOS level ioslevel Verify if system is vulnerable (AIX 7.2.5.0 through 7.2.5.212) if [[ $(oslevel -s) =~ ^7.2.5.[0-9]+$ ]]; then echo "Vulnerable AIX version detected" fi Check for installed fix (AIX example) instfix -ik IJ59566 Download fix from IBM Fix Central https://www.ibm.com/support/fixcentral Apply AIX Service Pack (example for 7.3 TL04 SP2) inutoc /path/to/SP smitty update_all Apply VIOS Fix Pack (example for 4.1.2.20) updateios -install /path/to/FP
Exploit: (Educational Purposes!)
A proof-of-concept for this vulnerability would involve crafting a malicious network packet or local input that triggers an out-of-bounds read in the affected AIX or VIOS component. The attacker would manipulate index values or buffer lengths to force the system to read memory beyond the allocated space. This can be achieved by sending specially crafted requests to a listening service on the target system. The out-of-bounds read may leak sensitive data such as cryptographic keys, memory addresses, or kernel structures, leading to further system compromise. In many cases, the read operation causes a segmentation fault, crashing the process and resulting in a denial of service.
Protection:
Apply the cumulative Service Packs (SPs) and Fix Packs (FPs) provided by IBM:
– AIX 7.3 TL04 SP2
– AIX 7.3 TL03 SP3
– AIX 7.3 TL02 SP5
– AIX 7.2 TL05 SP13
– VIOS 4.1.2 FP 4.1.2.20
– VIOS 4.1.1 FP 4.1.1.30
– VIOS 4.1.0 FP 4.1.0.50
An LPAR reboot is required to complete the update. On AIX, Live Update can be used to avoid a reboot. Special steps are required when using NIM to apply updates, and additional post-update instructions exist for VIOS 4.1.0 and 4.1.1 regarding migration to PostgreSQL 15.
Impact:
Successful exploitation allows a remote attacker to read sensitive information from system memory and cause a denial of service. The vulnerability has a high impact on confidentiality (C:H) and availability (A:H), with no impact on integrity (I:N). This could lead to exposure of critical system data, kernel secrets, or cryptographic material, and potentially render the system or virtual I/O server unresponsive, affecting all dependent logical partitions.
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Sources:
Reported By: nvd.nist.gov
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