CVE-2026-31504

Local privilege escalation via fanout re-registration race

Published Apr 22, 2026 · Updated Apr 22, 2026

Use-after-free in Linux Kernel branches starting with 3.1 allows local users to gain kernel privileges or crash the system through AF_PACKET fanout. packet_release() leaves po->num set while releasing a fanout socket, allowing concurrent NETDEV_UP handling to relink the socket in f->arr[] without increasing f->sk_ref and leave a dangling pointer. Exploitation requires CAP_NET_RAW and CAP_NET_ADMIN in the target network namespace, which unprivileged users can obtain through user and network namespaces on affected systems.

CVSS severity7.8
High
EPSS probability0.14%
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 Linux Kernel branches starting with 3.1 allows local users to gain kernel privileges or crash the system through AF_PACKET fanout. packet_release() leaves po->num set while releasing a fanout socket, allowing concurrent NETDEV_UP handling to relink the socket in f->arr[] without increasing f->sk_ref and leave a dangling pointer. Exploitation requires CAP_NET_RAW and CAP_NET_ADMIN in the target network namespace, which unprivileged users can obtain through user and network namespaces on affected systems.

The record

CVE
CVE-2026-31504
Published
Apr 22, 2026
Updated
Apr 22, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-416, T1068, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 22, 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=3.1
  2. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <1b4c03f8892d955385c202009af7485364731bb9
  3. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <42156f93d123436f2a27c468f18c966b7e5db796
  4. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <42cfd7898eeed290c9fb73f732af1f7d6b0a703e
  5. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <654386baef228c2992dbf604c819e4c7c35fc71b
  6. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <75fe6db23705a1d55160081f7b37db9665b1880b
  7. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <ceccbfc6de720ad633519a226715989cfb065af1
  8. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6
  9. Affected versionversion=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <ee642b1962caa9aa231c01abbd58bc453ae6b66e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3.1; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <1b4c03f8892d955385c202009af7485364731bb9; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <42156f93d123436f2a27c468f18c966b7e5db796; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <42cfd7898eeed290c9fb73f732af1f7d6b0a703e; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <654386baef228c2992dbf604c819e4c7c35fc71b; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <75fe6db23705a1d55160081f7b37db9665b1880b; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <ceccbfc6de720ad633519a226715989cfb065af1; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6; version=ce06b03e60fc19c680d1bf873e779bf11c2fc518 <ee642b1962caa9aa231c01abbd58bc453ae6b66e

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

CWE-416Use After Free
T1068Exploitation for Privilege Escalation
T1499.004Application or System Exploitation

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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