net: ipv6: flowlabel: defer exclusive option free until RCU teardown_CVE-2026-31680

{
    "lastseen": "",
    "description": "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->opt->opt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl->opt` as soon as `fl->users`\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->opt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU.",
    "published": "2026-04-25T08:46:56.807Z",
    "modified": "2026-04-27T14:05:00.799Z",
    "type": "cve",
    "title": "net: ipv6: flowlabel: defer exclusive option free until RCU teardown",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3\nhttps://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827\nhttps://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd\nhttps://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8\nhttps://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b\nhttps://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a\nhttps://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4\nhttps://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091",
    "id": "CVE-2026-31680",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499\nLinux Linux 3.9",
    "sourceHref": "",
    "cvss": {
        "score": 7.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
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        "confidentialityImpact": "",
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        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499",
    "vendor": "Linux",
    "ai_description": "",
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    "ai_score": 0
}