Description

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to obtain sensitive information due to an integer underflow in the IPv4 IP-options parser.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.4",
  "pubDate": "2026-08-19T20:17:05.030Z",
  "pubdate": "2026-08-19T20:17:05.030Z",
  "executiveSummary": "An information disclosure vulnerability exists in IBM AIX 7.2, 7.3, and IBM PowerVM VIOS 4.1, specifically within the IPv4 protocol handling subsystem. The root cause of this security defect is an integer underflow condition within the IPv4 IP-options parser. This flaw allows a remote, unauthenticated attacker to interact with the networking stack and potentially extract sensitive memory contents from the underlying operating system kernel or network buffers.\nThe risk implications are significant, as unauthorized exposure of kernel memory or system state data can facilitate the bypass of exploit mitigations such as Address Space Layout Randomization (ASLR), enabling subsequent advanced persistent attacks against the compromised host. Exploitation of this vulnerability requires network connectivity to the target system and relies on sending specially crafted IPv4 packets containing malicious IP options designed to trigger the arithmetic underflow during parsing routines. The vulnerability does not require prior authentication or elevated privileges, increasing its exposure profile within enterprise environments utilizing affected operating system versions.",
  "technicalDetails": "The vulnerability resides in the network stack of the affected operating systems, specifically inside the kernel-level parser responsible for processing incoming IPv4 options headers. During the evaluation of IPv4 packets containing malformed or edge-case IP options, the parser performs bounds calculations or length extractions without proper validation against the actual packet buffer boundaries. When a crafted IP options header specifies an invalid length parameter, an integer underflow occurs during subtraction or bounds checking operations.\nThis arithmetic underflow results in an integer wrap-around, transforming a small or negative value into an extremely large unsigned integer. Consequently, subsequent memory copy or pointer arithmetic operations within the IPv4 IP-options parser utilize this corrupted integer value. When the kernel attempts to read or parse the option fields based on the erroneous length calculation, it reads out-of-bounds memory from adjacent kernel heap or stack structures.\nThe attack flow proceeds as follows: 1) The remote attacker crafts a malicious IPv4 packet featuring an invalid or truncated IP options header designed to trigger the integer underflow condition. 2) The attacker transmits this packet over the network to the target running IBM AIX 7.2, 7.3, or IBM PowerVM VIOS 4.1. 3) The network interface driver passes the packet up to the IP layer, where the vulnerable IPv4 IP-options parser intercepts the packet for processing. 4) The parser evaluates the malformed options header, executing the vulnerable arithmetic calculation that triggers the integer underflow. 5) Due to the resulting incorrect buffer size evaluation, the parsing routine reads internal kernel memory structures. 6) The sensitive memory contents harvested via the out-of-bounds read are inadvertently exposed or reflected back through network responses or error-handling paths, allowing the remote attacker to harvest sensitive data.\nThe vulnerable component is the IPv4 packet processing engine handling IP options parsing within the kernel address space. The affected versions include IBM AIX 7.2, IBM AIX 7.3, and IBM PowerVM VIOS 4.1. The attack vector is strictly network-based, requiring no authentication or local execution privileges, exposing the network stack of any directly accessible interface processing IPv4 traffic."
}