CVE-2026-31662 (GCVE-0-2026-31662)
Vulnerability from cvelistv5
Published
2026-04-24 14:45
Modified
2026-04-27 14:04
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
Version: 2f487712b89376fce267223bbb0db93d393d4b09
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG\n\nThe GRP_ACK_MSG handler in tipc_group_proto_rcv() currently decrements\nbc_ackers on every inbound group ACK, even when the same member has\nalready acknowledged the current broadcast round.\n\nBecause bc_ackers is a u16, a duplicate ACK received after the last\nlegitimate ACK wraps the counter to 65535. Once wrapped,\ntipc_group_bc_cong() keeps reporting congestion and later group\nbroadcasts on the affected socket stay blocked until the group is\nrecreated.\n\nFix this by ignoring duplicate or stale ACKs before touching bc_acked or\nbc_ackers. This makes repeated GRP_ACK_MSG handling idempotent and\nprevents the underflow path."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
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      "providerMetadata": {
        "dateUpdated": "2026-04-27T14:04:47.160Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92"
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        {
          "url": "https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412"
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          "url": "https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8"
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        {
          "url": "https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3"
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        {
          "url": "https://git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6"
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          "url": "https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711"
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          "url": "https://git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682"
        },
        {
          "url": "https://git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8"
        }
      ],
      "title": "tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31662",
    "datePublished": "2026-04-24T14:45:12.593Z",
    "dateReserved": "2026-03-09T15:48:24.129Z",
    "dateUpdated": "2026-04-27T14:04:47.160Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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