CVE-2026-63559 describes an integer overflow vulnerability in the UA_Variant arrayDimensions product computation within the open62541 OPC UA library. A remote attacker could exploit this flaw to read out-of-bounds heap memory, potentially disclosing sensitive information. The vulnerability affects the open62541 open-source OPC UA implementation widely used in industrial and OT environments. CISA has issued an ICS advisory (ICSA-26-211-08) regarding this issue. Multiple pull requests and commits have been submitted to the open62541 GitHub repository to address the vulnerability. The flaw is remotely exploitable without authentication, increasing its severity. Affected organizations in critical infrastructure sectors should apply patches promptly.