CVE-2026-90111 (GCVE-0-2026-90111)
Vulnerability from cvelistv5
Published
2026-09-17 16:06
Modified
2026-10-30 12:34
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
ip6mr: do not clone dst in ip6mr_cache_report()
IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.
When an ingress multicast packet misses MFC lookup,
ip6mr_cache_unresolved() places the skb onto the unresolved queue,
escaping the receive-side RCU grace period.
If the underlying route is deleted and freed, and the MFC queue is later
resolved with a wrong parent interface, ip6_mr_forward() invokes
ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes
dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab
use-after-free.
Report packets queued to mroute6_sk (a raw socket) and netlink
notifications do not require an attached dst entry.
Fix this by:
1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs
do not hold a dst.
2. Dropping skb_dst before queuing unresolved skbs in
ip6mr_cache_unresolved(), matching the fact that multicast
forwarding resolves outgoing routes anew via ip6_route_output().
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 67f415dd29063a5906c560051c00e42dcf01a4dd Version: 67f415dd29063a5906c560051c00e42dcf01a4dd Version: 67f415dd29063a5906c560051c00e42dcf01a4dd Version: 67f415dd29063a5906c560051c00e42dcf01a4dd Version: 67f415dd29063a5906c560051c00e42dcf01a4dd Version: 67f415dd29063a5906c560051c00e42dcf01a4dd |
||
{
"containers": {
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{
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"product": "Linux",
"programFiles": [
"net/ipv6/ip6mr.c"
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"vendor": "Linux",
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"version": "6.6.160",
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{
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{
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"status": "unaffected",
"version": "6.18.57",
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{
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"status": "unaffected",
"version": "7.2.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"nodes": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6mr: do not clone dst in ip6mr_cache_report()\n\nIPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.\nWhen an ingress multicast packet misses MFC lookup,\nip6mr_cache_unresolved() places the skb onto the unresolved queue,\nescaping the receive-side RCU grace period.\n\nIf the underlying route is deleted and freed, and the MFC queue is later\nresolved with a wrong parent interface, ip6_mr_forward() invokes\nip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes\ndst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab\nuse-after-free.\n\nReport packets queued to mroute6_sk (a raw socket) and netlink\nnotifications do not require an attached dst entry.\n\nFix this by:\n1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs\n do not hold a dst.\n2. Dropping skb_dst before queuing unresolved skbs in\n ip6mr_cache_unresolved(), matching the fact that multicast\n forwarding resolves outgoing routes anew via ip6_route_output()."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The UAF is dst_clone(skb_dst(pkt)) in ip6mr_cache_report(MRT6MSG_WRONGMIF) on a NOREF dst that ip6_route_input() attached and ip6mr_cache_unresolved() queued past RCU. Completing it requires deleting that fib6 route and MRT6_ADD_MFC with mf6cc_parent != the arrival vif; those are local setsockopt/netlink from the same attacker, not a field in the IPv6 multicast datagram.\nAC:L - The attacker owns every step: MRT6_INIT/ADD_MIF/ASSERT, inject a non-link-local IPv6 multicast skb so ip6_mr_input() misses the MFC and ip6mr_cache_unresolved() queues it, delete the fib6 route and wait an RCU grace period, then MRT6_ADD_MFC with the wrong parent so ip6_mr_forward() takes the WRONGMIF path.\nPR:L - inet6_create() allows SOCK_RAW/IPPROTO_ICMPV6 only with ns_capable(CAP_NET_RAW); ip6_mroute_setsockopt() then lets that mroute socket (or ns_capable(CAP_NET_ADMIN)) run MRT6_ADD_MIF, MRT6_ASSERT, and MRT6_ADD_MFC. An unprivileged user obtains both capabilities in a user+net namespace via unshare -Urn.\nUI:N - The attacker opens the raw ICMPv6 mroute socket, adds MIFs, injects the multicast skb onto a veth, deletes the fib6 route, and installs the mismatched-parent MFC entirely with their own syscalls; no other user must mount a volume or otherwise interact.\nS:U - dst_clone()/dst_hold() touch the host kernel\u0027s struct dst_entry from the IPv6 fib looked up for the queued skb; the use-after-free stays in that networking authority and does not cross a VM, IOMMU, or other boundary.\nC:H - After the fib6 route is freed, ip6mr_cache_report() still does dst_clone(skb_dst(pkt)) and dst_hold() reads __rcuref on the dangling dst_entry; that slab UAF can be reclaimed with attacker-controlled objects and used as an arbitrary kernel read.\nI:H - dst_hold() calls rcuref_get(\u0026dst-\u003e__rcuref) on the freed dst_entry, writing a reclaimable slab object that can be sprayed to forge a refcount/control-flow hijack when the WRONGMIF report clones the stale dst.\nA:H - ip6_mr_forward() invoking ip6mr_cache_report(MRT6MSG_WRONGMIF) oopses in dst_hold()/rcuref_get() on the already-freed dst_entry even without a full exploit, so the bug is a reliable kernel crash as well as a UAF."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:34:13.088Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/b50d3cfb8513e895cee453dd0f834deee6ccc231"
},
{
"url": "https://git.kernel.org/stable/c/7f8287f606c8c028d4224e85d95dc448c6d6d623"
},
{
"url": "https://git.kernel.org/stable/c/42ef371466d5648f5c9e8bc219f0af0a2c2bbf8c"
},
{
"url": "https://git.kernel.org/stable/c/f57b0fd1c62e1be274ee154ab7fb8ac4481b7f89"
},
{
"url": "https://git.kernel.org/stable/c/4a674afaae4136c71943aa3e35d433676fd40e8f"
},
{
"url": "https://git.kernel.org/stable/c/235b42b5860189eb8c27c36435ad932cae65a734"
}
],
"title": "ip6mr: do not clone dst in ip6mr_cache_report()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-90111",
"datePublished": "2026-09-17T16:06:18.779Z",
"dateReserved": "2026-09-11T19:38:34.787Z",
"dateUpdated": "2026-10-30T12:34:13.088Z",
"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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