CVE-2026-31662

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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"}, 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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": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "a7db57ccca21f5801609065473c89a38229ecb92", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "575faea557f1a184a5f09661bd47ebd3ef3769f8", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "3bcf7aca63f0bcd679ae28e9b99823c608e59ce3", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "a2ea1ef0167d7a84730638d05c20ccdc421b14b6", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "1b6f13f626665cac67ba5a012765427680518711", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682", "versionType": "git"}, {"status": "affected", "version": "2f487712b89376fce267223bbb0db93d393d4b09", "lessThan": "48a5fe38772b6f039522469ee6131a67838221a8", "versionType": "git"}], "programFiles": ["net/tipc/group.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "4.15"}, {"status": "unaffected", "version": "0", "lessThan": "4.15", "versionType": "semver"}, {"status": "unaffected", "version": "5.10.253", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.203", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.169", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.135", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.82", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.18.23", "versionType": "semver", "lessThanOrEqual": "6.18.*"}, {"status": "unaffected", "version": "6.19.13", "versionType": "semver", "lessThanOrEqual": "6.19.*"}, {"status": "unaffected", "version": "7.0", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["net/tipc/group.c"], "defaultStatus": "affected"}], "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"}], "x_generator": {"engine": "bippy-1.2.0"}, "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."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.253", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.203", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.169", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.135", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.82", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.23", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.19.13", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.0", "versionStartIncluding": "4.15"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:12.893Z"}}}, "cveMetadata": {"cveId": "CVE-2026-31662", "state": "PUBLISHED", "dateUpdated": "2026-10-19T18:56:02.280Z", "dateReserved": "2026-03-09T15:48:24.129Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-04-24T14:45:12.593Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

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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."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ntipc: corregir el desbordamiento inferior de bc_ackers en GRP_ACK_MSG duplicados\n\nEl gestor GRP_ACK_MSG en tipc_group_proto_rcv() actualmente decrementa bc_ackers en cada ACK de grupo entrante, incluso cuando el mismo miembro ya ha acusado recibo de la ronda de difusi\u00f3n actual.\n\nDebido a que bc_ackers es un u16, un ACK duplicado recibido despu\u00e9s del \u00faltimo ACK leg\u00edtimo envuelve el contador a 65535. Una vez envuelto, tipc_group_bc_cong() sigue informando de congesti\u00f3n y las posteriores difusiones de grupo en el socket afectado permanecen bloqueadas hasta que el grupo es recreado.\n\nCorregir esto ignorando los ACKs duplicados u obsoletos antes de modificar bc_acked o bc_ackers. Esto hace que el manejo repetido de GRP_ACK_MSG sea idempotente y previene la ruta de desbordamiento inferior."}], "id": "CVE-2026-31662", "lastModified": "2026-11-11T23:10:00.263", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-31662", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:11:44.605157Z", "version": "2.0.3"}}]}, "published": "2026-04-24T15:16:45.820", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a2ea1ef0167d7a84730638d05c20ccdc421b14b6"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a7db57ccca21f5801609065473c89a38229ecb92"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e0bb732eaf77f9ac2f2638bdac9e39b81e0a9682"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-191"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-190"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG", "id": "2461491", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461491"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-191", "details": ["A flaw was found in the Linux kernel's Transparent Inter-Process Communication (TIPC) protocol. An attacker can exploit an integer underflow vulnerability by sending duplicate group acknowledgment messages (GRP_ACK_MSG). This causes the `bc_ackers` counter to wrap around, leading to persistent network congestion. Consequently, group broadcasts on the affected socket become blocked, resulting in a denial of service until the group is manually recreated."], "name": "CVE-2026-31662", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31662\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31662\nhttps://lore.kernel.org/linux-cve-announce/2026042404-CVE-2026-31662-3728@gregkh/T"], "threat_severity": "Moderate"}

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