CVE-2026-7770: IBM i Access Client Solutions (ACS) is vulnerable to remote code execution when configured to listen for requests from IBM i Navigator

Synopsis

Remote code execution vulnerability in IBM i Access Client Solutions (ACS), affecting versions 1.1.5.0 through 1.1.9.12. The flaw is reachable over the network by any authenticated low-privilege user, with no victim interaction required, when ACS is configured to listen for requests from IBM i Navigator. Successful exploitation gives an attacker full control over confidentiality, integrity, and availability of the affected system. HarborGuard is tracking the IBM advisory and will make a patched-image rebuild available as soon as IBM publishes a fix version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable service must be reachable over the network; an attacker sends malicious requests to ACS while it is listening for IBM i Navigator connections.

• AuthenticationRequired

  Any low-privilege authenticated account is sufficient; no administrative or elevated credentials are needed to trigger the vulnerability.

• Victim interactionNot required

  No user action or social engineering is needed; the attacker exploits the listening service directly without any interaction from a victim.

• Attack complexityDetail

  The exploit is reliable and condition-free, requiring no race conditions, specific memory layout, or other environmental factors beyond network access and credentials.

Blast Radius

• A successful attacker executes arbitrary code in the context of the ACS process, gaining a foothold on the host running IBM i Access Client Solutions.
• All data accessible to the ACS process, including stored credentials, configuration files, and session data, is readable by the attacker.
• The attacker can modify or delete files, configuration, and persisted data accessible to the ACS process.
• The attacker can crash or permanently disrupt the ACS service and any dependent IBM i Navigator workflows relying on it.