CVE-2025-39984

Invalid kernel read via stale TUN skb pointer

Published Oct 15, 2025 · Updated May 11, 2026

Use-after-free in the Linux kernel TUN driver 6.9 allows local users to trigger an invalid memory read through a TUN device. When generic XDP replaces and frees an skb in skb_pp_cow_data(), tun_get_user() leaves napi->skb pointing to the freed buffer before GRO reuses it. Reachability requires TUN access and an attached XDP program; the stale pointer can expose freed kernel memory, corrupt state, or crash the host.

CVSS severity7.3
High
EPSS probability0.20%
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 Linux kernel TUN driver 6.9 allows local users to trigger an invalid memory read through a TUN device. When generic XDP replaces and frees an skb in skb_pp_cow_data(), tun_get_user() leaves napi->skb pointing to the freed buffer before GRO reuses it. Reachability requires TUN access and an attached XDP program; the stale pointer can expose freed kernel memory, corrupt state, or crash the host.

The record

CVE
CVE-2025-39984
Published
Oct 15, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 15, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=6.9
  2. Affected versionversion=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <1091860a16a86ccdd77c09f2b21a5f634f5ab9ec
  3. Affected versionversion=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <1697577e1669b0321d02cd848384a5d33e284296
  4. Affected versionversion=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <953200d56fc23eebf80a5ad9eed6e2e8a3065093

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.9; version=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <1091860a16a86ccdd77c09f2b21a5f634f5ab9ec; version=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <1697577e1669b0321d02cd848384a5d33e284296; version=e6d5dbdd20aa6a86974af51deb9414cd2e7794cb <953200d56fc23eebf80a5ad9eed6e2e8a3065093

Published CVSS scores

7.3Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/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

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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