CVE-2026-99121

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-99121", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.393Z", "datePublished": "2026-10-28T10:34:37.082Z", "dateUpdated": "2026-10-30T12:41:56.754Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-30T12:41:56.754Z"}, "descriptions": [{"lang": "en", "value": "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/ipv4/fib_semantics.c"], "versions": [{"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "baf3a767b2845eb8e68f056ee4aa5b41b151e990", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "f655a26490e705ec76a79db7f412847fda342b39", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "7c68f4de5090b17b63b9a0a3b01b3807e01a296a", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "226a974054acbd892560bfa67f0ae8ffe271a736", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "0800c92ca5d1983df6843a5435299978901d1d02", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "d5520e815c4b1427104ce1428ee23821f2aa824d", "status": "affected", "versionType": "git"}, {"version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "lessThan": "5046d2880fec7d49ebed2fd2866747ee1d06ad71", "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/ipv4/fib_semantics.c"], "versions": [{"version": "4.4", "status": "affected"}, {"version": "0", "lessThan": "4.4", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.273", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.224", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.191", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.161", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.115", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.59", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.13", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3", "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": "4.4", "versionEndExcluding": "5.10.273"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "5.15.224"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.1.191"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.6.161"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.12.115"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.18.59"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "7.2.13"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/baf3a767b2845eb8e68f056ee4aa5b41b151e990"}, {"url": "https://git.kernel.org/stable/c/f655a26490e705ec76a79db7f412847fda342b39"}, {"url": "https://git.kernel.org/stable/c/7c68f4de5090b17b63b9a0a3b01b3807e01a296a"}, {"url": "https://git.kernel.org/stable/c/226a974054acbd892560bfa67f0ae8ffe271a736"}, {"url": "https://git.kernel.org/stable/c/0800c92ca5d1983df6843a5435299978901d1d02"}, {"url": "https://git.kernel.org/stable/c/5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f"}, {"url": "https://git.kernel.org/stable/c/d5520e815c4b1427104ce1428ee23821f2aa824d"}, {"url": "https://git.kernel.org/stable/c/5046d2880fec7d49ebed2fd2866747ee1d06ad71"}], "title": "ipv4: avoid divide by zero in fib_rebalance", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/ipv4/fib_semantics.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "baf3a767b2845eb8e68f056ee4aa5b41b151e990", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "f655a26490e705ec76a79db7f412847fda342b39", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "7c68f4de5090b17b63b9a0a3b01b3807e01a296a", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "226a974054acbd892560bfa67f0ae8ffe271a736", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "0800c92ca5d1983df6843a5435299978901d1d02", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "d5520e815c4b1427104ce1428ee23821f2aa824d", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}, {"lessThan": "5046d2880fec7d49ebed2fd2866747ee1d06ad71", "status": "affected", "version": "0e884c78ee19e902f300ed147083c28a0c6302f0", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["net/ipv4/fib_semantics.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "4.4"}, {"lessThan": "4.4", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.273", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.224", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.191", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.161", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.115", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.59", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.13", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-99121", "lastModified": "2026-10-30T13:21:46.377", "metrics": {}, "published": "2026-10-28T11:17:31.733", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/0800c92ca5d1983df6843a5435299978901d1d02"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/226a974054acbd892560bfa67f0ae8ffe271a736"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/5046d2880fec7d49ebed2fd2866747ee1d06ad71"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7c68f4de5090b17b63b9a0a3b01b3807e01a296a"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/baf3a767b2845eb8e68f056ee4aa5b41b151e990"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/d5520e815c4b1427104ce1428ee23821f2aa824d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f655a26490e705ec76a79db7f412847fda342b39"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: kernel: Denial of Service via division by zero during IPv4 route rebalancing", "id": "2562713", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2562713"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-369", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nipv4: avoid divide by zero in fib_rebalance\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.\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.", "A flaw was found in the Linux kernel's IPv4 networking component. A race condition in the fib_rebalance() function can cause a division-by-zero error when routing configurations change concurrently during route rebalancing. A local user or concurrent network event can trigger this flaw, causing the kernel to crash and resulting in a Denial of Service (DoS)."], "name": "CVE-2026-99121", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-10-28T10:34:37Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-99121\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-99121\nhttps://git.kernel.org/stable/c/5046d2880fec7d49ebed2fd2866747ee1d06ad71\nhttps://git.kernel.org/stable/c/5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f\nhttps://git.kernel.org/stable/c/d5520e815c4b1427104ce1428ee23821f2aa824d"], "threat_severity": "Moderate"}

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