CVE-2026-31680 (GCVE-0-2026-31680)
Vulnerability from cvelistv5
Published
2026-04-25 08:46
Modified
2026-04-27 14:05
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In 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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 Version: d3aedd5ebd4b0b925b0bcda548066803e1318499 |
||
{
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"version": "0",
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"status": "unaffected",
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{
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"status": "unaffected",
"version": "5.15.203",
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},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.168",
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{
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"version": "6.6.134",
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"version": "6.12.81",
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{
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],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"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"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-27T14:05:00.799Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"references": [
{
"url": "https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3"
},
{
"url": "https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"
},
{
"url": "https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd"
},
{
"url": "https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8"
},
{
"url": "https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b"
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{
"url": "https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a"
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{
"url": "https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4"
},
{
"url": "https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091"
}
],
"title": "net: ipv6: flowlabel: defer exclusive option free until RCU teardown",
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}
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"cveMetadata": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-31680",
"datePublished": "2026-04-25T08:46:56.807Z",
"dateReserved": "2026-03-09T15:48:24.130Z",
"dateUpdated": "2026-04-27T14:05:00.799Z",
"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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