CVE-2026-31680

Local kernel crash via flowlabel use-after-free

Published Apr 25, 2026 · Updated Apr 25, 2026

Use-after-free in the IPv6 flowlabel code in Linux Kernel allows local users to crash the kernel through a concurrent procfs read. fl_release() frees fl->opt before the enclosing ip6_flowlabel leaves the global hash, so ip6fl_seq_show() can dereference reclaimed option state. Low privileges through a user namespace can satisfy the option-state gate, and no victim action is needed; the observed consequence is an oops or crash, while reclaimed heap contents can also be exposed or attacker-shaped.

CVSS severity7.8
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the IPv6 flowlabel code in Linux Kernel allows local users to crash the kernel through a concurrent procfs read. fl_release() frees fl->opt before the enclosing ip6_flowlabel leaves the global hash, so ip6fl_seq_show() can dereference reclaimed option state. Low privileges through a user namespace can satisfy the option-state gate, and no victim action is needed; the observed consequence is an oops or crash, while reclaimed heap contents can also be exposed or attacker-shaped.

The record

CVE
CVE-2026-31680
Published
Apr 25, 2026
Updated
Apr 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.9
  2. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <3c54b66c83fb8fcbde8e6a7bf90b65856e39f827
  3. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <414726b69921fe6355ae453f5b35e68dd078342a
  4. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <4b6798024f7b2d535f3db1002c760143cdbd1bd3
  5. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <572ce62778519a7d4d1c15f55dd2e45a474133c4
  6. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <5a6b15f861b7c1304949e3350d23490a5fe429fd
  7. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <6c7fbdb8ffde6413640de7cfbd7c976c353e89f8
  8. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <8027964931785cb73d520ac70a342a3dc16c249b
  9. Affected versionversion=d3aedd5ebd4b0b925b0bcda548066803e1318499 <9ca562bb8e66978b53028fa32b1a190708e6a091

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3.9; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <3c54b66c83fb8fcbde8e6a7bf90b65856e39f827; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <414726b69921fe6355ae453f5b35e68dd078342a; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <4b6798024f7b2d535f3db1002c760143cdbd1bd3; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <572ce62778519a7d4d1c15f55dd2e45a474133c4; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <5a6b15f861b7c1304949e3350d23490a5fe429fd; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <6c7fbdb8ffde6413640de7cfbd7c976c353e89f8; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <8027964931785cb73d520ac70a342a3dc16c249b; version=d3aedd5ebd4b0b925b0bcda548066803e1318499 <9ca562bb8e66978b53028fa32b1a190708e6a091

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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