CVE-2026-31662

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

• linux linux kernel (>= 4.15.1 < 5.10.253) • linux linux kernel (>= 5.11 < 5.15.203) • linux linux kernel (>= 5.16 < 6.1.169) • linux linux kernel (>= 6.2 < 6.6.135) • linux linux kernel (>= 6.7 < 6.12.82) • linux linux kernel (>= 6.13 < 6.18.23) • linux linux kernel (>= 6.19 < 6.19.13) • linux linux kernel 4.15 • linux linux kernel 7.0