CVE-2026-99074
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: stop PMTU walk when nexthop group shrinks Commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") made __ip_rt_update_pmtu() update every path. For nexthop objects, fib_info_num_path() and fib_info_nhc() independently load nh->nh_grp. RCU protects each group's lifetime but does not make the loads observe the same group. If replacement shrinks the group after the loop accepts an index, fib_info_nhc() returns NULL and update_or_create_fnhe() dereferences it. A deterministic probe only widened the existing window between the real operations. On v7.2, an RTM_NEWNEXTHOP replacement published a one-member group after the PMTU reader accepted index 1 from a two-member group, producing: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: update_or_create_fnhe+0x45/0x15b0 Stop when the indexed path is absent. Groups are dense, so no later index exists in that snapshot. The same real-writer window completed 114,423 PMTU iterations without an oops with this check. A reproducer is available on request. Replacement requires CAP_NET_ADMIN in the network namespace. Where unprivileged user namespaces are permitted, a local user can obtain it in a new user and network namespace.
Severity
Not scored
CVSS score
Not available
Vulnerability status
Received
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-10-23 13:17:31.397000
Last modified
2026-10-30 13:21:43.640000
View original CVE JSON
{
"id": "CVE-2026-99074",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-23T13:17:31.397",
"lastModified": "2026-10-30T13:21:43.640",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: stop PMTU walk when nexthop group shrinks\n\nCommit 7d3f3b4367f3 (\"net: ipv4: Cache pmtu for all packet paths if\nmultipath enabled\") made __ip_rt_update_pmtu() update every path.\n\nFor nexthop objects, fib_info_num_path() and fib_info_nhc()\nindependently load nh->nh_grp. RCU protects each group's lifetime but\ndoes not make the loads observe the same group. If replacement shrinks\nthe group after the loop accepts an index, fib_info_nhc() returns NULL\nand update_or_create_fnhe() dereferences it.\n\nA deterministic probe only widened the existing window between the real\noperations. On v7.2, an RTM_NEWNEXTHOP replacement published a\none-member group after the PMTU reader accepted index 1 from a two-member\ngroup, producing:\n\n KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n RIP: update_or_create_fnhe+0x45/0x15b0\n\nStop when the indexed path is absent. Groups are dense, so no later\nindex exists in that snapshot. The same real-writer window completed\n114,423 PMTU iterations without an oops with this check. A reproducer\nis available on request.\n\nReplacement requires CAP_NET_ADMIN in the network namespace. Where\nunprivileged user namespaces are permitted, a local user can obtain it\nin a new user and network namespace."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/ipv4/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "fc07a232326a623d0be482e307c08ea7049c2846",
"lessThan": "82d83eec893d8ae84f280aec44c60d9fdecc62b5",
"versionType": "git",
"status": "affected"
},
{
"version": "b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e",
"lessThan": "a411df69524f91fe3adb8f9544d33e701fc9732c",
"versionType": "git",
"status": "affected"
},
{
"version": "3bed2abab4a682d426624ce9add9d7b6d475d4e4",
"lessThan": "7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a",
"versionType": "git",
"status": "affected"
},
{
"version": "7f5005457b3072fe1ddf15bfef869f2a1d98e05e",
"lessThan": "c60d17d6dd61adc761ac6f65a008fefbc54cbf87",
"versionType": "git",
"status": "affected"
},
{
"version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
"lessThan": "c6d670ac656badfd0e15355e07a13a6bdf3b69fd",
"versionType": "git",
"status": "affected"
},
{
"version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
"lessThan": "f27483f9975b5065ff67054cc7eb8edac6083488",
"versionType": "git",
"status": "affected"
},
{
"version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
"lessThan": "6619e01855e65ef35723685a557e3eb106f4ecf5",
"versionType": "git",
"status": "affected"
},
{
"version": "5.15.179",
"lessThan": "5.15.224",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.1.129",
"lessThan": "6.1.191",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.6.79",
"lessThan": "6.6.160",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.12.16",
"lessThan": "6.12.113",
"versionType": "semver",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/ipv4/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "6.13",
"status": "affected"
},
{
"version": "0",
"lessThan": "6.13",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.224",
"lessThanOrEqual": "5.15.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.191",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.160",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.113",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.57",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.11",
"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/6619e01855e65ef35723685a557e3eb106f4ecf5",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}