CVE-2026-31662: tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG
In the Linux kernel, the following vulnerability has been resolved:
tipc: fix bcackers underflow on duplicate GRPACKMSG
The GRPACKMSG handler in tipcgroupprotorcv() currently decrements bcackers on every inbound group ACK, even when the same member has already acknowledged the current broadcast round.
Because bcackers is a u16, a duplicate ACK received after the last legitimate ACK wraps the counter to 65535. Once wrapped, tipcgroupbccong() 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 bcacked or bcackers. This makes repeated GRPACKMSG handling idempotent and prevents the underflow path.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-31662?
CVE-2026-31662 is classified as a low-severity vulnerability affecting the Linux kernel.
How do I fix CVE-2026-31662?
To address CVE-2026-31662, update your Linux kernel to a patched version provided by your distribution.
What systems are affected by CVE-2026-31662?
CVE-2026-31662 affects the Linux kernel, specifically versions prior to the fix for the tipc_group_proto_rcv function.
What type of vulnerability is CVE-2026-31662?
CVE-2026-31662 is a programming error vulnerability that involves an underflow in the processing of duplicate group acknowledgment messages.
Is there any exploit available for CVE-2026-31662?
There are currently no known exploits for CVE-2026-31662 in the wild, but it is still advisable to apply the fix.