CVE-2026-31662

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG<br /> <br /> The GRP_ACK_MSG handler in tipc_group_proto_rcv() currently decrements<br /> bc_ackers on every inbound group ACK, even when the same member has<br /> already acknowledged the current broadcast round.<br /> <br /> Because bc_ackers is a u16, a duplicate ACK received after the last<br /> legitimate ACK wraps the counter to 65535. Once wrapped,<br /> tipc_group_bc_cong() keeps reporting congestion and later group<br /> broadcasts on the affected socket stay blocked until the group is<br /> recreated.<br /> <br /> Fix this by ignoring duplicate or stale ACKs before touching bc_acked or<br /> bc_ackers. This makes repeated GRP_ACK_MSG handling idempotent and<br /> prevents the underflow path.