An unsigned integer underflow exists in the signature verification path of the PubSub component in o6 Automation’s open62541 library. When a specially crafted packet is received over UDP, the underflow can corrupt internal state and cause the library to abort, resulting in a crash of the process that uses it. The flaw leads to a denial of service but does not affect confidentiality or integrity of other data handled by the system.

Any deployment that includes the open62541 library with its PubSub over UDP implementation is at risk. The vendor list notes o6 Automation as the affected vendor, and no specific product version is mentioned, implying that builds containing the vulnerable code path are affected. Systems relying on open62541 for industrial control or automation message passing should investigate whether the PubSub feature is enabled and the network topology exposes the UDP endpoints.

The CVSS score of 8.2 indicates a high severity vulnerability that can be exploited remotely through a crafted UDP packet. The EPSS score of 2% suggests a modest but non‑negligible likelihood of exploitation in the wild. The vulnerability is not yet listed in CISA’s KEV catalog, meaning there are no confirmed large‑scale exploit campaigns as of the last update. An attacker does not need privileged access or advanced prerequisites; a single packet from an external source is sufficient to trigger the denial of service.