CVE-2026-99074 (GCVE-0-2026-99074)
Vulnerability from cvelistv5
Published
2026-10-23 12:23
Modified
2026-10-30 12:41
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: fc07a232326a623d0be482e307c08ea7049c2846 Version: b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e Version: 3bed2abab4a682d426624ce9add9d7b6d475d4e4 Version: 7f5005457b3072fe1ddf15bfef869f2a1d98e05e Version: 7d3f3b4367f315a61fc615e3138f3d320da8c466 Version: 7d3f3b4367f315a61fc615e3138f3d320da8c466 Version: 7d3f3b4367f315a61fc615e3138f3d320da8c466 Version: 5.15.179 ≤ Version: 6.1.129 ≤ Version: 6.6.79 ≤ Version: 6.12.16 ≤ |
||
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"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-\u003enh_grp. RCU protects each group\u0027s 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."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:41:33.126Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"url": "https://git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5"
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{
"url": "https://git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c"
},
{
"url": "https://git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a"
},
{
"url": "https://git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87"
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{
"url": "https://git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd"
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{
"url": "https://git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488"
},
{
"url": "https://git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5"
}
],
"title": "ipv4: stop PMTU walk when nexthop group shrinks",
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"assignerShortName": "Linux",
"cveId": "CVE-2026-99074",
"datePublished": "2026-10-23T12:23:17.866Z",
"dateReserved": "2026-09-25T10:25:14.389Z",
"dateUpdated": "2026-10-30T12:41:33.126Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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