Advisory · CVE-2026-6730
Buffer overflow in IBM Concert allows local code execution
Improper bounds checking in IBM Concert 1.0.0 through 3.0.0 lets a local user overflow a buffer and execute arbitrary code on the system.
- Vendor
- IBM
- Product
- IBM Concert
- Identifier / CWE
- CVE-2026-6730
CWE-120 - Action timing
- Immediate
Explain it like I’m five
The app pours user input into a fixed-size cup without checking how much it pours. The overflow spills onto the instructions the computer follows next, letting a local user rewrite them.
- 01Local access
An attacker has local user access to a system running IBM Concert 1.0.0 through 3.0.0.
- 02Oversized input
The attacker supplies input larger than the destination buffer, which the application does not bounds-check.
- 03Memory corruption
The overflow corrupts adjacent memory, including control data.
- 04Code execution
The attacker redirects execution to arbitrary code in the context of the affected process.
What happened
IBM Concert versions 1.0.0 through 3.0.0 are vulnerable to a buffer overflow caused by improper bounds checking. A local user can overflow the buffer and execute arbitrary code on the system. IBM rates the issue critical at CVSS 9.8 in its security bulletin, which covers this flaw alongside CVE-2026-6721 and CVE-2026-6928.
What to do
- Follow the IBM security bulletin for remediation and apply it to all Concert deployments.
- Limit local access to Concert hosts to trusted operators until remediated.
- Review system logs for crashes or anomalous process behavior on Concert hosts.
- Investigate any Concert host where untrusted local users had access.
Management note
This is one of three same-day memory safety and injection flaws in IBM Concert, all rated 9.8. The cluster suggests the codebase needs a broader hardening review, not just point patches. Prioritize the unauthenticated remote flaw (CVE-2026-6721) first, then close out the local ones.