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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.

PUBLISHED Reserved 2026-03-09 | Published 2026-04-24 | Updated 2026-04-27 | Assigner Linux




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Product status

Default status
unaffected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before a7db57ccca21f5801609065473c89a38229ecb92
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before 575faea557f1a184a5f09661bd47ebd3ef3769f8
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before a2ea1ef0167d7a84730638d05c20ccdc421b14b6
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before 1b6f13f626665cac67ba5a012765427680518711
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682
affected

2f487712b89376fce267223bbb0db93d393d4b09 (git) before 48a5fe38772b6f039522469ee6131a67838221a8
affected

Default status
affected

4.15
affected

Any version before 4.15
unaffected

5.10.253 (semver)
unaffected

5.15.203 (semver)
unaffected

6.1.169 (semver)
unaffected

6.6.135 (semver)
unaffected

6.12.82 (semver)
unaffected

6.18.23 (semver)
unaffected

6.19.13 (semver)
unaffected

7.0 (original_commit_for_fix)
unaffected

References

git.kernel.org/...c/a7db57ccca21f5801609065473c89a38229ecb92

git.kernel.org/...c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412

git.kernel.org/...c/575faea557f1a184a5f09661bd47ebd3ef3769f8

git.kernel.org/...c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3

git.kernel.org/...c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6

git.kernel.org/...c/1b6f13f626665cac67ba5a012765427680518711

git.kernel.org/...c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682

git.kernel.org/...c/48a5fe38772b6f039522469ee6131a67838221a8

cve.org (CVE-2026-31662)

nvd.nist.gov (CVE-2026-31662)

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