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.

No CVSS v4.0

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Linux Linux unaffected
Version Status Constraints
2f487712b89376fce267223bbb0db93d393d4b09 affected < a7db57ccca21f5801609065473c89a38229ecb92
2f487712b89376fce267223bbb0db93d393d4b09 affected < 36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412
2f487712b89376fce267223bbb0db93d393d4b09 affected < 575faea557f1a184a5f09661bd47ebd3ef3769f8
2f487712b89376fce267223bbb0db93d393d4b09 affected < 3bcf7aca63f0bcd679ae28e9b99823c608e59ce3
2f487712b89376fce267223bbb0db93d393d4b09 affected < a2ea1ef0167d7a84730638d05c20ccdc421b14b6
2f487712b89376fce267223bbb0db93d393d4b09 affected < 1b6f13f626665cac67ba5a012765427680518711
2f487712b89376fce267223bbb0db93d393d4b09 affected < e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682
2f487712b89376fce267223bbb0db93d393d4b09 affected < 48a5fe38772b6f039522469ee6131a67838221a8
Linux Linux affected
Version Status Constraints
4.15 affected —
0 unaffected < 4.15
5.10.253 unaffected ≤ 5.10.*
5.15.203 unaffected ≤ 5.15.*
6.1.169 unaffected ≤ 6.1.*
6.6.135 unaffected ≤ 6.6.*
6.12.82 unaffected ≤ 6.12.*
6.18.23 unaffected ≤ 6.18.*
6.19.13 unaffected ≤ 6.19.*
7.0 unaffected ≤ *

No data.

No data.

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711 cve-icon cve-icon
https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412 cve-icon cve-icon
https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3 cve-icon cve-icon
https://git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8 cve-icon cve-icon
https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8 cve-icon cve-icon
https://git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6 cve-icon cve-icon
https://git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92 cve-icon cve-icon
https://git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682 cve-icon cve-icon
https://lore.kernel.org/linux-cve-announce/2026042404-CVE-2026-31662-3728@gregkh/T cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-31662 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-31662 cve-icon
History

Sat, 25 Apr 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-191
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate

Fri, 24 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
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.
Title tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-04-24T14:45:12.593Z

Reserved: 2026-03-09T15:48:24.129Z

Link: CVE-2026-31662

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-04-24T15:16:45.820

Modified: 2026-04-24T17:51:40.810

Link: CVE-2026-31662

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-04-24T00:00:00Z

Links: CVE-2026-31662 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses