Linux Kernel up to 6.17.8 mlx5_add_cq_to_tasklet initialization

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.17.8. It has been declared as critical. Impacted is the function mlx5_add_cq_to_tasklet. Executing a manipulation can lead to initialization. This vulnerability appears as CVE-2025-68209. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.17.8 and classified as critical. This vulnerability affects the function mlx5_add_cq_to_tasklet. The manipulation with an unknown input leads to a initialization vulnerability. The CWE definition for the vulnerability is CWE-665. The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mlx5: Fix default values in create CQ Currently, CQs without a completion function are assigned the mlx5_add_cq_to_tasklet function by default. This is problematic since only user CQs created through the mlx5_ib driver are intended to use this function. Additionally, all CQs that will use doorbells instead of polling for completions must call mlx5_cq_arm. However, the default CQ creation flow leaves a valid value in the CQ's arm_db field, allowing FW to send interrupts to polling-only CQs in certain corner cases. These two factors would allow a polling-only kernel CQ to be triggered by an EQ interrupt and call a completion function intended only for user CQs, causing a null pointer exception. Some areas in the driver have prevented this issue with one-off fixes but did not address the root cause. This patch fixes the described issue by adding defaults to the create CQ flow. It adds a default dummy completion function to protect against null pointer exceptions, and it sets an invalid command sequence number by default in kernel CQs to prevent the FW from sending an interrupt to the CQ until it is armed. User CQs are responsible for their own initialization values. Callers of mlx5_core_create_cq are responsible for changing the completion function and arming the CQ per their needs.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2025-68209 since 12/16/2025. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 02/21/2026).

The vulnerability scanner Nessus provides a plugin with the ID 296481 (SUSE SLES15 Security Update : kernel (SUSE-SU-2026:0278-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.9 eliminates this vulnerability. Applying the patch 08469f5393a1a39f26a6e2eb2e8c33187665c1f4/e5eba42f01340f73888dfe560be2806057c25913 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 (296481) and CERT Bund (WID-SEC-2025-2868). Once again VulDB remains the best source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7
• 6.17.8

License

• open-source

Website

• Vendor: https://www.kernel.org/

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