Description

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote authenticated attacker to overwrite adjacent memory due to an integer underflow during bounds checking.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.5",
  "pubDate": "2026-08-19T21:16:54.270Z",
  "pubdate": "2026-08-19T21:16:54.270Z",
  "executiveSummary": "An integer underflow vulnerability affecting IBM i versions 7.6, 7.5, 7.4, and 7.3 permits a remote authenticated attacker to overwrite adjacent memory structures.\nThe flaw stems from flawed arithmetic logic during boundary validation routines, specifically failing to properly account for integer underflow conditions.\nSuccessful exploitation of this memory corruption vulnerability can lead to localized denial of service conditions, unpredictable system behavior, or potential arbitrary memory manipulation depending on the surrounding execution context.\nThe threat actor must possess valid authentication credentials to interact with the vulnerable system component remotely.\nGiven the severity of memory overwrite primitives in enterprise operating systems, organizations running affected IBM i deployments face significant integrity and availability risks if unauthorized or malicious users leverage valid credentials to trigger the fault condition.\nRemediation requires applying official vendor-supplied software fixes or security PTFs as designated by IBM to correct the bounds checking logic.",
  "technicalDetails": "The vulnerability is rooted in an integer underflow condition that occurs during bounds checking operations within the affected IBM i operating system components across versions 7.6, 7.5, 7.4, and 7.3.\nDuring memory allocation or buffer validation routines, the software performs arithmetic operations to verify that requested sizes or indices fall within safe boundaries.\nWhen manipulated input or specific operational states cause an integer underflow, the resulting value wraps around to an unexpectedly large integer.\nBecause the underlying validation logic interprets this wrapped integer as a valid, small, or within-bounds value, the subsequent bounds check improperly passes.\nThis flawed verification allows read or write operations to exceed the intended buffer limits, resulting in out-of-bounds memory access and the overwriting of adjacent memory blocks.\nAttack execution requires the threat actor to have remote network access combined with valid system authentication credentials, indicating a privilege requirement associated with standard user access levels.\nBy supplying carefully crafted inputs that trigger the integer underflow during targeted system interactions, the authenticated attacker can manipulate heap or stack memory layouts adjacent to the vulnerable buffer.\nThe resulting memory corruption can corrupt critical data structures, crash system daemons, or induce unstable runtime conditions leading to denial of service.\nPost-exploitation impact is constrained by the privileges of the authenticated session, but severe corruption of kernel or system-level memory spaces can jeopardize overall host integrity."
}