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CVE-2026-16924 is a remotely exploitable denial of service vulnerability affecting IBM AIX versions 7.2 and 7.3, as well as IBM PowerVM VIOS version 4.1. The root cause lies in an improper calculation of a memory offset during IPsec decapsulation. When the operating system or virtualization I/O server processes a specially crafted IPsec packet, the flawed offset calculation causes the system to reference an incorrect memory location. This can lead to memory corruption, a system panic, or an unresponsive kernel state, effectively crashing the targeted system.
The vulnerability is triggered over the network by an unauthenticated attacker. No user interaction is required, and the attack complexity is low, making it relatively easy to exploit. The issue stems from an incorrect calculation of buffer size (CWE-131) and an integer underflow (CWE-191) during the IPsec decapsulation process. When the system attempts to reassemble or validate the incoming packet, the miscalculated memory offset causes the system to read or write outside the intended buffer boundaries. This results in memory corruption that can destabilize the kernel and force a system crash.
IBM has assigned a CVSS v3.1 base score of 7.5 (HIGH) to this vulnerability, with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. The attack vector is remote (AV:N), the attack complexity is low (AC:L), no privileges are required (PR:N), and no user interaction is needed (UI:N). The scope is unchanged (S:U), with no impact on confidentiality (C:N) or integrity (I:N), but a high impact on availability (A:H). This makes CVE-2026-16924 a serious threat to production AIX and VIOS environments, as a single crafted packet can knock a critical system offline.
DailyCVE Form:
Platform: IBM AIX / PowerVM VIOS
Version: 7.2, 7.3, 4.1
Vulnerability: Improper memory offset calculation
Severity: HIGH (7.5 CVSS)
Date: August 20, 2026
Prediction: Patch expected August 14, 2026
What Undercode Say:
Check AIX version oslevel -s Check VIOS version ioslevel Verify if system is vulnerable (AIX 7.2, 7.3 or VIOS 4.1) AIX 7.2 TL05 SP13 or higher is patched AIX 7.3 TL04 SP2, TL03 SP3, TL02 SP5 or higher are patched VIOS 4.1.2.20, 4.1.1.30, 4.1.0.50 or higher are patched Check installed filesets for IPsec-related components lslpp -L | grep -i ipsec Monitor for kernel panic logs errpt -a | grep -i panic Check for system crashes who -b uptime
Exploit: (Educational Purposes!)
The following is a conceptual representation of how an attacker might trigger the vulnerability. A remote unauthenticated attacker crafts a malicious IPsec packet with manipulated decapsulation headers that cause an integer underflow (CWE-191) in the memory offset calculation. This forces the kernel to read/write outside the intended buffer, leading to a system panic. Crafting the packet requires deep knowledge of the IPsec implementation in AIX/VIOS. The attack is performed over the network with low complexity and no authentication. Example of a malformed IPsec packet structure (conceptual): [IP Header] -> [ESP Header] -> [Malformed Payload with manipulated length fields] Upon receipt, the vulnerable function calculates an offset using the manipulated length, causing an integer underflow (CWE-191) and subsequent out-of-bounds memory access (CWE-131). The result is a kernel panic and denial of service. This exploit is remote, unauthenticated, and requires no user interaction.
Protection:
- Apply the following IBM-recommended Service Packs and Fix Packs immediately:
- 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
- VIOS 4.1.0.50
- Download fixes from IBM Fix Central: https://www.ibm.com/support/fixcentral
- An LPAR reboot is required to complete the update; on AIX, Live Update can be used to avoid a reboot
- If unable to patch immediately, restrict network access to IPsec services and monitor for suspicious traffic patterns
- Regularly review IBM security advisories for additional mitigations
Impact:
- System Availability: Successful exploitation causes a kernel panic or system crash, resulting in a complete denial of service. The affected system becomes unresponsive and requires a manual reboot to restore operations.
- Business Continuity: For production AIX and VIOS environments hosting critical enterprise workloads, an unpatched system is at risk of being taken offline by a single crafted network packet. This can lead to significant downtime and operational disruption.
- No Data Breach: The vulnerability does not compromise confidentiality or integrity; it solely affects availability. However, repeated exploitation can render systems unusable until patched.
- Wide Exposure: The attack is remote, unauthenticated, and requires no user interaction. Any system with IPsec enabled and exposed to untrusted networks is vulnerable.
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Sources:
Reported By: nvd.nist.gov
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