{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-31662", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.129Z", "datePublished": "2026-04-24T14:45:12.593Z", "dateUpdated": "2026-08-05T12:24:12.893Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:12.893Z" }, "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": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable handler processes TIPC GROUP_PROTOCOL messages received over configured TIPC bearers, including UDP/IP bearers that accept network packets from peer nodes. A malicious remote TIPC peer can send crafted or duplicate GRP_ACK_MSG packets to the victim group socket.\nAC:L - There is no race or hard-to-control condition; after joining or appearing as a group member, the attacker can send an ACK and then a stale or duplicate ACK with a new link sequence number. The triggering state is a normal replicast group broadcast with ACKs enabled.\nPR:N - The attacker does not need privileges on the victim system; TIPC discovery/group protocol messages are accepted from network peers after normal bearer/node establishment, with no mandatory authentication in the vulnerable path. Optional TIPC crypto or deployment filtering is not required for the vulnerable code path.\nUI:N - No victim user action is required once the vulnerable TIPC group service is running. The attacker triggers the bug by sending network protocol messages.\nS:U - The impact remains within the same kernel/TIPC communication security authority. There is no VM escape, sandbox escape, or cross-authority boundary bypass.\nC:N - The bug is a logical u16 counter underflow in group broadcast ACK accounting, not a memory disclosure or memory corruption primitive. It does not provide a way to read confidential data.\nI:N - The attacker corrupts protocol accounting state only to block later broadcasts; there is no unauthorized data modification, arbitrary write, or control-flow impact. The security consequence is denial of service rather than integrity compromise.\nA:H - Wrapping bc_ackers to 65535 makes tipc_group_bc_cong() keep reporting congestion, so subsequent group broadcasts on the affected socket remain blocked until the group is recreated. In a TIPC-based clustered or control deployment this is a persistent, remotely triggerable loss of availability for the affected communication channel." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/tipc/group.c" ], "versions": [ { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "a7db57ccca21f5801609065473c89a38229ecb92", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "575faea557f1a184a5f09661bd47ebd3ef3769f8", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "3bcf7aca63f0bcd679ae28e9b99823c608e59ce3", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "a2ea1ef0167d7a84730638d05c20ccdc421b14b6", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "1b6f13f626665cac67ba5a012765427680518711", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682", "status": "affected", "versionType": "git" }, { "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "48a5fe38772b6f039522469ee6131a67838221a8", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/tipc/group.c" ], "versions": [ { "version": "4.15", "status": "affected" }, { "version": "0", "lessThan": "4.15", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.253", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.203", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.169", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.135", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.82", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.23", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.13", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "5.10.253" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "5.15.203" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "6.1.169" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "6.6.135" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "6.12.82" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "6.18.23" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "6.19.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "7.0" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92" }, { "url": "https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412" }, { "url": "https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8" }, { "url": "https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3" }, { "url": "https://git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6" }, { "url": "https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711" }, { "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", "x_generator": { "engine": "bippy-1.2.0" } } } }