Quick answers
- Is CVE-2026-16821 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-16821 being exploited in the wild.
- How severe is CVE-2026-16821?
- High severity, with a CVSS score of 7, published 28 August 2026.
- Which products and versions are affected?
- IBM Aix 7.2, 7.3; IBM PowerVM VIOS 4.1.
- Is there a fix for CVE-2026-16821?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-16821 attacked?
- It is attacked with local access.
- Am I affected by CVE-2026-16821?
- Check whether you run IBM Aix or IBM PowerVM VIOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A format string vulnerability exists in IBM AIX 7.2, 7.3 and PowerVM VIOS 4.1, where user-controlled input is passed unsafely to a format string function in a privileged system component. This vulnerability requires local access and existing user privileges to exploit. An attacker can craft a malicious input containing format string specifiers to read arbitrary memory, write to arbitrary memory locations, or execute arbitrary code with the privileges of the affected process. Patches are available through IBM service packs and fix packs as documented in IBM's security bulletin.
Affected products
- IBM AIX 7.2, 7.3
- IBM PowerVM VIOS 4.1
Timeline
- 2026-08-28: disclosed