GHSA-2XWR-GH6X-HM86
Vulnerability from github – Published: 2026-04-25 09:30 – Updated: 2026-10-15 03:35In the Linux kernel, the following vulnerability has been resolved:
net: ipv6: flowlabel: defer exclusive option free until RCU teardown
ip6fl_seq_show() walks the global flowlabel hash under the seq-file
RCU read-side lock and prints fl->opt->opt_nflen when an option block
is present.
Exclusive flowlabels currently free fl->opt as soon as fl->users
drops to zero in fl_release(). However, the surrounding
struct ip6_flowlabel remains visible in the global hash table until
later garbage collection removes it and fl_free_rcu() finally tears it
down.
A concurrent /proc/net/ip6_flowlabel reader can therefore race that
early kfree() and dereference freed option state, triggering a crash
in ip6fl_seq_show().
Fix this by keeping fl->opt alive until fl_free_rcu(). That matches
the lifetime already required for the enclosing flowlabel while readers
can still reach it under RCU.
{
"affected": [],
"aliases": [
"CVE-2026-31680"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-25T09:16:01Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: flowlabel: defer exclusive option free until RCU teardown\n\n`ip6fl_seq_show()` walks the global flowlabel hash under the seq-file\nRCU read-side lock and prints `fl-\u003eopt-\u003eopt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl-\u003eopt` as soon as `fl-\u003eusers`\ndrops to zero in `fl_release()`. However, the surrounding\n`struct ip6_flowlabel` remains visible in the global hash table until\nlater garbage collection removes it and `fl_free_rcu()` finally tears it\ndown.\n\nA concurrent `/proc/net/ip6_flowlabel` reader can therefore race that\nearly `kfree()` and dereference freed option state, triggering a crash\nin `ip6fl_seq_show()`.\n\nFix this by keeping `fl-\u003eopt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU.",
"id": "GHSA-2xwr-gh6x-hm86",
"modified": "2026-10-15T03:35:44Z",
"published": "2026-04-25T09:30:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31680"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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