CVE-2026-17423 is a high severity (CVSS 7.7) out-of-bounds read in IBM AIX 7.2 and 7.3 and PowerVM VIOS 4.1. IBM says a remote attacker could obtain sensitive information and cause a denial of service. The fix is the cumulative service pack or fix pack IBM lists for each level.
What's affected
IBM AIX 7.2 and 7.3, and IBM PowerVM VIOS 4.1. IBM's bulletin is a shared one that lists many AIX and VIOS vulnerabilities, and its change history shows an initial publication on 15 August 2026. The affected fileset is bos.mp64 at these levels:
- AIX 7.2.5: 7.2.5.0 to 7.2.5.212
- AIX 7.3.2: 7.3.2.0 to 7.3.2.5
- AIX 7.3.3: 7.3.3.0 to 7.3.3.2
- AIX 7.3.4: 7.3.4.0 to 7.3.4.1
IBM's remediation levels are AIX 7.2 TL05 SP13, 7.3 TL02 SP5, 7.3 TL03 SP3 and 7.3 TL04 SP2, and VIOS fix packs 4.1.0.50, 4.1.1.30 and 4.1.2.20. These service packs are cumulative. IBM lists no workaround or mitigation.
How to check if you're exposed
Check the AIX level and the affected fileset on each LPAR.
oslevel -s
lslpp -L | grep -i bos.mp64
On a VIOS, run ioslevel as padmin. If the bos.mp64 level falls in one of the ranges above, the system is affected. IBM also assigns APARs: IJ59566 for AIX 7.2.5, IJ59565 for 7.3.2, IJ59564 for 7.3.3 and IJ59563 for 7.3.4.
What to do now
- List every AIX LPAR and VIOS, with its technology level and service pack.
- Download the service pack or fix pack for your level from IBM Fix Central.
- Plan the LPAR reboot, or use Live Update on AIX where it fits, because IBM says a reboot is needed to complete the update.
- Read IBM's notes on nimsh secure and, for VIOS 4.1.0 and 4.1.1, the post-update steps for the Postgres15 migration.
- Recheck
oslevel -safter the update and record it.
Why it matters
The weakness is CWE-125 (Out-of-bounds Read). Reading outside a buffer can expose data from other parts of memory and may crash the process. IBM names information disclosure and denial of service.
One detail stands out. IBM describes a remote attacker, yet the CVSS vector in the record gives the attack vector as local. Read the vector as IBM's scoring of the realistic path, and do not assume that low exposure removes the need to patch. High impact is listed for confidentiality and availability. CISA does not list this CVE as known exploited.
Quick check
The description says remote but the vector says local. Why?
The record gives both. IBM describes a remote attacker in the text, while the vector scores the attack vector as local. Patch on the basis of the fix being available and cheap, not on this difference.
Sources
Last reviewed: 19 October 2026.
