{"id":"CVE-2026-99121","aliases":[],"title":"ipv4: avoid divide by zero in fib_rebalance","titleSource":"Linux","descriptionSource":"Linux","products":[{"vendor":"Linux","name":"Linux","platforms":[],"versions":[{"version":"0e884c78ee19e902f300ed147083c28a0c6302f0","status":"affected","lessThan":"5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f","versionType":"git"},{"version":"0e884c78ee19e902f300ed147083c28a0c6302f0","status":"affected","lessThan":"d5520e815c4b1427104ce1428ee23821f2aa824d","versionType":"git"},{"version":"0e884c78ee19e902f300ed147083c28a0c6302f0","status":"affected","lessThan":"5046d2880fec7d49ebed2fd2866747ee1d06ad71","versionType":"git"}],"defaultStatus":"unaffected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99121"},{"vendor":"Linux","name":"Linux","platforms":[],"versions":[{"version":"4.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.4","versionType":"semver"},{"version":"6.18.59","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"defaultStatus":"affected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99121"}],"remediation":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: avoid divide by zero in fib_rebalance\n\nfib_rebalance() computes the total eligible nexthop weight in one pass\nand programs upper bounds in a second pass. A concurrent change to\nignore_routes_with_linkdown can make the first pass return zero while\nthe second pass sees an eligible nexthop, resulting in division by zero.\n\nIf the first pass reports a zero total, set each nexthop upper bound to\n-1 and skip the division. This matches the IPv6 fix in commit\nd2c26c2911dd (\"ipv6: avoid divide by zero in rt6_multipath_rebalance\")\nand preserves the lock-free rebalance path.","severity":"unknown","score":null,"published":"2026-10-28T10:34:37.082Z","modified":"2026-10-28T10:34:37.082Z","withdrawn":false,"knownExploited":false,"affected":[],"references":["https://git.kernel.org/stable/c/5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f","https://git.kernel.org/stable/c/d5520e815c4b1427104ce1428ee23821f2aa824d","https://git.kernel.org/stable/c/5046d2880fec7d49ebed2fd2866747ee1d06ad71"],"sources":[{"name":"CVE","id":"CVE-2026-99121","modified":"2026-10-28T10:34:37.082Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-99121"}],"assessments":[],"sourceAffected":[],"kev":{"status":"not-listed","checkedAt":"2026-10-29T00:30:33.731Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}