AIX: Out-of-bounds Read
CVE-2026-16839 is a critical-severity out-of-bounds read vulnerability in AIX from IBM, with a CVSS 3.1 base score of 9.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected AIX versions: 7.2; 7.3. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.52% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Vios to 4.1.0.50 or 4.1.1.30 or 4.1.2.20, whichever matches your release line, or a later version.
- Read the advisory on ibm.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| IBM | AIX | 7.2; 7.3 | Not stated |
| IBM | PowerVM VIOS | 4.1 | Not stated |
| IBM | Vios | 4.1.0 up to, but not including, 4.1.0.50; 4.1.1.0 up to, but not including, 4.1.1.30; 4.1.2.0 up to, but not including, 4.1.2.20 | 4.1.0.50, 4.1.1.30, 4.1.2.20 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H. Scored by CNA (us.ibm.com).
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in AIX
- 7.8 High severity
- 8.8 High severity
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
Recent Out-of-bounds Read vulnerabilities
- 8.1 High severity
- 7.3 High severity
- 8.2 High severity
- 7.6 High severity
- 7.1 High severity
- 8.2 High severity
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