Linux Kernel up to 6.6.135/6.12.83/6.18.24/7.0.1 tpacket_snd toctou

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CTI Interest Score
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6.1$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.6.135/6.12.83/6.18.24/7.0.1. It has been classified as critical. This impacts the function tpacket_snd. This manipulation causes toctou. The identification of this vulnerability is CVE-2026-31700. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.6.135/6.12.83/6.18.24/7.0.1 and classified as critical. Affected by this vulnerability is the function tpacket_snd. The manipulation with an unknown input leads to a toctou vulnerability. The CWE definition for the vulnerability is CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd() In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points directly into the mmap'd TX ring buffer shared with userspace. The kernel validates the header via __packet_snd_vnet_parse() but then re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent userspace thread can modify the vnet_hdr fields between validation and use, bypassing all safety checks. The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr to a stack-local variable. All other vnet_hdr consumers in the kernel (tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX path is the only caller of virtio_net_hdr_to_skb() that reads directly from user-controlled shared memory. Fix this by copying vnet_hdr from the mmap'd ring buffer to a stack-local variable before validation and use, consistent with the approach used in packet_snd() and all other callers.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-31700 since 03/09/2026. The exploitation appears to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 317729 (SUSE SLES12 Security Update : kernel (SUSE-SU-2026:2068-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.136, 6.12.84, 6.18.25, 7.0.2 or 7.1-rc1 eliminates this vulnerability. Applying the patch 74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121/3a1bf9116ea31470b89692585c3910dfe830dcdd/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b/2c054e17d9d41f1020376806c7f750834ced4dc5 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (317729) and CERT Bund (WID-SEC-2026-1346). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux
  • Microsoft Azure Linux
  • Red Hat OpenShift

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.2
VulDB Meta Temp Score: 6.1

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.8
CNA Vector (Linux): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Toctou
CWE: CWE-367 / CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 317729
Nessus Name: SUSE SLES12 Security Update : kernel (SUSE-SU-2026:2068-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.136/6.12.84/6.18.25/7.0.2/7.1-rc1
Patch: 74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121/3a1bf9116ea31470b89692585c3910dfe830dcdd/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b/2c054e17d9d41f1020376806c7f750834ced4dc5

Timelineinfo

03/09/2026 CVE reserved
05/01/2026 +52 days Advisory disclosed
05/01/2026 +0 days VulDB entry created
06/30/2026 +60 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-31700 (🔒)
GCVE (CVE): GCVE-0-2026-31700
GCVE (VulDB): GCVE-100-360589
CERT Bund: WID-SEC-2026-1346 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 05/01/2026 16:42
Updated: 06/30/2026 19:56
Changes: 05/01/2026 16:42 (58), 05/04/2026 14:10 (7), 05/30/2026 14:41 (2), 06/09/2026 10:07 (1), 06/20/2026 21:55 (11), 06/30/2026 19:56 (3)
Complete: 🔍
Cache ID: 216::103

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