CVE-2026-52940

Kernel-stack disclosure via uninitialized TUN header

Published Jun 24, 2026 · Updated Jun 24, 2026

Information disclosure in the Linux Kernel TUN driver allows local users to read 14 bytes of kernel-stack data per non-tunnel packet. tun_put_user() allocates a 24-byte virtio_net_hdr_v1_hash_tunnel structure without zeroing it, while virtio_net_hdr_tnl_from_skb() initializes only the first 10 bytes. A local user with low privileges must set the virtual-network header size to 24 with TUNSETVNETHDRSZ and read a non-tunnel packet; __tun_vnet_hdr_put() then returns the remaining 14 bytes of kernel-stack contents.

CVSS severity5.5
Medium
EPSS probability0.16%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Linux Kernel TUN driver allows local users to read 14 bytes of kernel-stack data per non-tunnel packet. tun_put_user() allocates a 24-byte virtio_net_hdr_v1_hash_tunnel structure without zeroing it, while virtio_net_hdr_tnl_from_skb() initializes only the first 10 bytes. A local user with low privileges must set the virtual-network header size to 24 with TUNSETVNETHDRSZ and read a non-tunnel packet; __tun_vnet_hdr_put() then returns the remaining 14 bytes of kernel-stack contents.

The record

CVE
CVE-2026-52940
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 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=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <585cb85e9a29185be05f326369573c2663cf4380
  2. Affected versionversion=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5
  3. Affected versionversion=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <7f2fcff15e99bb852f6967396ed12b38376e2c8d
  4. Affected versionversion=6.17

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <585cb85e9a29185be05f326369573c2663cf4380; version=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5; version=288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 <7f2fcff15e99bb852f6967396ed12b38376e2c8d; version=6.17

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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

T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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