CVE-2026-31700

Safety-check bypass via mutable vnet header

Published May 1, 2026 · Updated May 1, 2026

Race condition in Linux Kernel net/packet allows local users to bypass header safety checks through a concurrent TX-ring write. In tpacket_snd(), the kernel validates vnet_hdr in a shared memory-mapped ring and later rereads its fields in virtio_net_hdr_to_skb instead of preserving the validated values. Low-privileged local access and PACKET_VNET_HDR on a memory-mapped TPACKET TX ring are required; the public record does not specify the resulting kernel action.

CVSS severity7.8
High
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux Kernel net/packet allows local users to bypass header safety checks through a concurrent TX-ring write. In tpacket_snd(), the kernel validates vnet_hdr in a shared memory-mapped ring and later rereads its fields in virtio_net_hdr_to_skb instead of preserving the validated values. Low-privileged local access and PACKET_VNET_HDR on a memory-mapped TPACKET TX ring are required; the public record does not specify the resulting kernel action.

The record

CVE
CVE-2026-31700
Published
May 1, 2026
Updated
May 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 1, 2026CVE publishedPublication date reported by the CVE source.
  2. May 1, 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=1d036d25e5609ba73fee6a88db01c306b140d512 <28324a3b62d9ce7f9bdd65a8ce63f382041d1b27
  2. Affected versionversion=1d036d25e5609ba73fee6a88db01c306b140d512 <2c054e17d9d41f1020376806c7f750834ced4dc5
  3. Affected versionversion=1d036d25e5609ba73fee6a88db01c306b140d512 <3a1bf9116ea31470b89692585c3910dfe830dcdd
  4. Affected versionversion=1d036d25e5609ba73fee6a88db01c306b140d512 <48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b
  5. Affected versionversion=1d036d25e5609ba73fee6a88db01c306b140d512 <74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121
  6. Affected versionversion=4.6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1d036d25e5609ba73fee6a88db01c306b140d512 <28324a3b62d9ce7f9bdd65a8ce63f382041d1b27; version=1d036d25e5609ba73fee6a88db01c306b140d512 <2c054e17d9d41f1020376806c7f750834ced4dc5; version=1d036d25e5609ba73fee6a88db01c306b140d512 <3a1bf9116ea31470b89692585c3910dfe830dcdd; version=1d036d25e5609ba73fee6a88db01c306b140d512 <48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b; version=1d036d25e5609ba73fee6a88db01c306b140d512 <74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121; version=4.6

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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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