CVE-2026-31662: Linux Kernel

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux Kernel: from 4.15.1, before 5.10.253 (fixed in 5.10.253); from 5.11, before 5.15.203 (fixed in 5.15.203); from 5.16, before 6.1.169 (fixed in 6.1.169); from 6.2, before 6.6.135 (fixed in 6.6.135); from 6.7, before 6.12.82 (fixed in 6.12.82); from 6.13, before 6.18.23 (fixed in 6.18.23); …

Published 2026-04-24. Last modified 2026-06-17.