{"cve":"CVE-2026-31662","nvd":{"published":"2026-04-24T15:16:45.820","modified":"2026-10-19T19:18:03.737","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-191","CWE-190"],"references":["https://git.kernel.org/stable/c/1b6f13f626665cac67ba5a012765427680518711","https://git.kernel.org/stable/c/36ec4fdd6250dcd5e73eb09ea92ed92e9cc28412","https://git.kernel.org/stable/c/3bcf7aca63f0bcd679ae28e9b99823c608e59ce3","https://git.kernel.org/stable/c/48a5fe38772b6f039522469ee6131a67838221a8","https://git.kernel.org/stable/c/575faea557f1a184a5f09661bd47ebd3ef3769f8"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-31662","score":0.00389,"percentile":0.32703,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}