tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG

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Summary

CVECVE-2026-31662
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-24 15:16:45 UTC
Updated2026-04-27 20:17:55 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.000240000 probability, percentile 0.067850000 (date 2026-04-27)

Problem Types: CWE-191

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 a7db57ccca21f5801609065473c89a38229ecb92 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 575faea557f1a184a5f09661bd47ebd3ef3769f8 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 a2ea1ef0167d7a84730638d05c20ccdc421b14b6 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 1b6f13f626665cac67ba5a012765427680518711 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682 git Not specified
CNA Linux Linux affected 2f487712b89376fce267223bbb0db93d393d4b09 48a5fe38772b6f039522469ee6131a67838221a8 git Not specified
CNA Linux Linux affected 4.15 Not specified
CNA Linux Linux unaffected 4.15 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.169 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.135 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.82 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.23 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.13 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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