Linux Kernel up to 6.6.123/6.12.69/6.18.9 Tun Driver udp4_gro_complete injection

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.4	$0-$5k	0.00

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.6.123/6.12.69/6.18.9 and classified as critical. Affected by this vulnerability is the function udp4_gro_complete of the component Tun Driver. This manipulation causes injection. This vulnerability is handled as CVE-2026-23254. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.6.123/6.12.69/6.18.9 and classified as critical. Affected by this vulnerability is the function udp4_gro_complete of the component Tun Driver. The manipulation with an unknown input leads to a injection vulnerability. The CWE definition for the vulnerability is CWE-74. The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: gro: fix outer network offset The udp GRO complete stage assumes that all the packets inserted the RX have the `encapsulation` flag zeroed. Such assumption is not true, as a few H/W NICs can set such flag when H/W offloading the checksum for an UDP encapsulated traffic, the tun driver can inject GSO packets with UDP encapsulation and the problematic layout can also be created via a veth based setup. Due to the above, in the problematic scenarios, udp4_gro_complete() uses the wrong network offset (inner instead of outer) to compute the outer UDP header pseudo checksum, leading to csum validation errors later on in packet processing. Address the issue always clearing the encapsulation flag at GRO completion time. Such flag will be set again as needed for encapsulated packets by udp_gro_complete().

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-23254 since 01/13/2026. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/02/2026). The attack technique deployed by this issue is T1055 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 315738 (Ubuntu 22.04 LTS / 24.04 LTS : Linux kernel vulnerabilities (USN-8278-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.124, 6.12.70 or 6.18.10 eliminates this vulnerability. Applying the patch 9d40a85138568696387ef04cd004c64612a70874/b83557bc6f560433fe5d727e241069f8db5ba709/2e5edb69e5d0e23ef248c56fc977039268c77a7b/5c2c3c38be396257a6a2e55bd601a12bb9781507 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 (315738) and CERT Bund (WID-SEC-2026-0790). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.6.123
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.12.20
• 6.12.21
• 6.12.22
• 6.12.23
• 6.12.24
• 6.12.25
• 6.12.26
• 6.12.27
• 6.12.28
• 6.12.29
• 6.12.30
• 6.12.31
• 6.12.32
• 6.12.33
• 6.12.34
• 6.12.35
• 6.12.36
• 6.12.37
• 6.12.38
• 6.12.39
• 6.12.40
• 6.12.41
• 6.12.42
• 6.12.43
• 6.12.44
• 6.12.45
• 6.12.46
• 6.12.47
• 6.12.48
• 6.12.49
• 6.12.50
• 6.12.51
• 6.12.52
• 6.12.53
• 6.12.54
• 6.12.55
• 6.12.56
• 6.12.57
• 6.12.58
• 6.12.59
• 6.12.60
• 6.12.61
• 6.12.62
• 6.12.63
• 6.12.64
• 6.12.65
• 6.12.66
• 6.12.67
• 6.12.68
• 6.12.69
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
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CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

Class: Injection
CWE: CWE-74 / CWE-707 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 315738
Nessus Name: Ubuntu 22.04 LTS / 24.04 LTS : Linux kernel vulnerabilities (USN-8278-1)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.124/6.12.70/6.18.10
Patch: 9d40a85138568696387ef04cd004c64612a70874/b83557bc6f560433fe5d727e241069f8db5ba709/2e5edb69e5d0e23ef248c56fc977039268c77a7b/5c2c3c38be396257a6a2e55bd601a12bb9781507

Timelineinfo

01/13/2026 CVE reserved
03/18/2026 +64 days Advisory disclosed
03/18/2026 +0 days VulDB entry created
06/02/2026 +76 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-23254 (🔒)
GCVE (CVE): GCVE-0-2026-23254
GCVE (VulDB): GCVE-100-351571
CERT Bund: WID-SEC-2026-0790 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 03/18/2026 19:46
Updated: 06/02/2026 14:49
Changes: 03/18/2026 19:46 (59), 03/19/2026 19:26 (7), 03/24/2026 17:52 (1), 05/21/2026 22:25 (2), 06/02/2026 14:49 (10)
Complete: 🔍
Cache ID: 216::103

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Discussion

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