CVE-2026-31680 (GCVE-0-2026-31680)

Vulnerability from cvelistv5 – Published: 2026-04-25 08:46 – Updated: 2026-04-27 14:05
VLAI?
Title
net: ipv6: flowlabel: defer exclusive option free until RCU teardown
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.
Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 4b6798024f7b2d535f3db1002c760143cdbd1bd3 (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 5a6b15f861b7c1304949e3350d23490a5fe429fd (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 8027964931785cb73d520ac70a342a3dc16c249b (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 414726b69921fe6355ae453f5b35e68dd078342a (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 572ce62778519a7d4d1c15f55dd2e45a474133c4 (git)
Affected: d3aedd5ebd4b0b925b0bcda548066803e1318499 , < 9ca562bb8e66978b53028fa32b1a190708e6a091 (git)
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    Linux Linux Affected: 3.9
Unaffected: 0 , < 3.9 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "net/ipv6/ip6_flowlabel.c"
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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    "dateReserved": "2026-03-09T15:48:24.130Z",
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.