CVE-2026-6730 is a buffer overflow in IBM Concert versions 1.0.0 through 3.0.0, rated critical (CVSS 9.8), that can let an attacker run arbitrary code on the affected system.
What Is It
IBM reports that IBM Concert has a buffer overflow caused by improper bounds checking. The weakness is classified as CWE-120 (Buffer Copy without Checking Size of Input, the "classic buffer overflow"). According to the vendor description, a local user could overflow the buffer and execute arbitrary code on the system.
IBM PSIRT submitted the record, and NVD published it on 2026-09-23. Its NVD status is currently "Received," which means NVD has not yet done its own analysis.
Why It Matters
IBM PSIRT gave the flaw a CVSS 3.1 base score of 9.8 (CRITICAL) with this vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
That vector describes a network-reachable, low-complexity attack that needs no privileges or user interaction. A successful attack fully compromises confidentiality, integrity, and availability.
Note the conflict: the written description says a local user could exploit the flaw, but the CVSS vector says it can be exploited over the network with no privileges. Until IBM clarifies which is correct, defenders should plan for the worse case in the score.
Exploitation status: CVE-2026-6730 does not appear in the supplied CISA Known Exploited Vulnerabilities (KEV) data. KEV does not confirm active exploitation at this time.
What's Vulnerable
- Vendor: IBM
- Product: Concert
- Affected versions: 1.0.0 through 3.0.0 inclusive (semver)
The CPE entries in the record cover cpe:2.3:a:ibm:concert:1.0.0 and cpe:2.3:a:ibm:concert:3.0.0, and the version range covers everything between them.
Patch Status
The supplied NVD record does not name a fixed version or specific remediation steps. IBM links to a security bulletin on its support portal, and administrators should go there for patch and upgrade guidance. There is no CISA KEV entry, so no federal remediation deadline or required action applies right now.
Recommended actions based on the available data:
- Find every IBM Concert deployment running versions 1.0.0 through 3.0.0.
- Read IBM's bulletin and apply the fix or upgrade it lists.
- Until you have patched, treat affected instances as critical given the 9.8 score.
Sources
- NVD – CVE-2026-6730
- IBM Security Bulletin (node 7288830)
- CISA Known Exploited Vulnerabilities Catalog (no entry for this CVE at time of writing)