CVE-2026-99121
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: avoid divide by zero in fib_rebalance fib_rebalance() computes the total eligible nexthop weight in one pass and programs upper bounds in a second pass. A concurrent change to ignore_routes_with_linkdown can make the first pass return zero while the second pass sees an eligible nexthop, resulting in division by zero. If the first pass reports a zero total, set each nexthop upper bound to -1 and skip the division. This matches the IPv6 fix in commit d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") and preserves the lock-free rebalance path.
Severity
Not scored
CVSS score
Not available
Vulnerability status
Received
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-10-28 11:17:31.733000
Last modified
2026-10-30 13:21:46.377000
View original CVE JSON
{
"id": "CVE-2026-99121",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-28T11:17:31.733",
"lastModified": "2026-10-30T13:21:46.377",
"vulnStatus": "Received",
"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."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/ipv4/fib_semantics.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "0e884c78ee19e902f300ed147083c28a0c6302f0",
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"versionType": "git",
"status": "affected"
},
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},
{
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"defaultStatus": "affected",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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},
{
"version": "0",
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"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.273",
"lessThanOrEqual": "5.10.*",
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"status": "unaffected"
},
{
"version": "5.15.224",
"lessThanOrEqual": "5.15.*",
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"status": "unaffected"
},
{
"version": "6.1.191",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.161",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.115",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.59",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.13",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/0800c92ca5d1983df6843a5435299978901d1d02",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
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{
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}