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CVE-2026-16883 is an out-of-bounds read vulnerability affecting IBM AIX 7.2, AIX 7.3, and IBM PowerVM VIOS 4.1. The flaw resides in a system-level component — likely the AIX kernel or a privileged device driver interface — that fails to validate memory boundary conditions when handling requests from unprivileged local users.
An out-of-bounds read (CWE-125) occurs when a program accesses memory outside the intended buffer boundaries. In this case, a local attacker with low privileges can trigger the vulnerable code path, causing the system to read data from adjacent memory regions that should be inaccessible. Because the attacker has only low privileges (PR:L), the vulnerable component must be exposed to unprivileged processes — typically through a system call, ioctl, or administrative utility that fails to properly validate input parameters.
The information exposed may include authentication tokens, encryption keys, memory contents belonging to other processes or users, or other sensitive kernel-space data. This breaks the security boundary between unprivileged users and protected system data, potentially enabling privilege escalation or further compromise of the system. The attack requires local access — the attacker must already have a valid user account on the target system — and there is no known remote exploitation pathway.
IBM has assigned APARs (Authorized Program Analysis Reports) to track the fix for each affected version: IJ5956608 for AIX 7.2.5, IJ5956508 for AIX 7.3.2, IJ5956408 for AIX 7.3.3, IJ5956308 for AIX 7.3.4, and corresponding APARs for VIOS 4.1.0, 4.1.1, and 4.1.2. Remediation requires applying the appropriate Service Pack (SP) for AIX or Fix Pack (FP) for VIOS, with an LPAR reboot required to complete the update (though AIX Live Update can avoid a reboot).
DailyCVE Form:
Platform: IBM AIX / PowerVM VIOS
Version: 7.2, 7.3 / 4.1
Vulnerability: Out-of-bounds Read
Severity: MEDIUM (CVSS 5.5)
Date: 2026-08-19
Prediction: Patch available 2026-08-14
What Undercode Say:
Check AIX version oslevel -s Check VIOS version ioslevel Check if APAR is installed instfix -ik IJ5956608 AIX 7.2.5 instfix -ik IJ5956508 AIX 7.3.2 instfix -ik IJ5956408 AIX 7.3.3 instfix -ik IJ5956308 AIX 7.3.4 Check VIOS APAR instfix -ik IJ5956508 VIOS 4.1.0 instfix -ik IJ5956408 VIOS 4.1.1 instfix -ik IJ5956308 VIOS 4.1.2 List all installed filesets with APAR info lslpp -L -q all | grep -i apar Download fixes from IBM Fix Central https://www.ibm.com/support/fixcentral
Exploit: (Educational Purposes!)
A local attacker with a valid user account can trigger the out-of-bounds read by invoking a vulnerable system call or device driver interface that does not validate input boundaries. The flaw allows reading memory beyond the allocated buffer, potentially exposing sensitive kernel or hypervisor data. No public exploit code has been confirmed in the CISA KEV catalog.
Example trigger pattern (conceptual - not a working exploit) The vulnerability is triggered through a privileged system call or administrative utility that fails to validate boundary conditions Attacker with low privileges (PR:L) executes: ./trigger_vulnerable_component --offset <out_of_bounds_value> Result: reads adjacent memory regions exposing sensitive data such as authentication tokens, encryption keys, or other process memory
Protection:
IBM has released fixes available via Fix Central:
| Affected Version | Required Fix |
|||
| AIX 7.3 TL04 | SP2 |
| AIX 7.3 TL03 | SP3 |
| AIX 7.3 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 |
These Service Packs and Fix Packs are cumulative and include fixes for all previously published AIX/VIOS security vulnerabilities. An LPAR reboot is required to complete the update.
Impact:
- Confidentiality: High impact — a local attacker can read sensitive information from memory, including credentials, encryption keys, and data belonging to other processes or users
- Integrity: None — the vulnerability does not allow modification of data
- Availability: None — the vulnerability does not cause denial of service
- Attack Vector: Local — the attacker must already have a valid user account on the target system
- Privileges Required: Low — the attacker does not need elevated privileges
- User Interaction: None — the vulnerability can be triggered without user involvement
- Scope: Unchanged — the impact is confined to the vulnerable component
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Sources:
Reported By: nvd.nist.gov
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