Description
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
References8
- git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711 Patch
- git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 Patch
- git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3 Patch
- git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8 Patch
- git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8 Patch
- git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6 Patch
- git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92 Patch
- git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682 Patch
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 34 · as of 13 November 2026
- CWE
- CWE-191CWE-190
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