Linux Kernel up to 6.18.2/6.19-rc1 refcount_t lib/refcount.c _mlx5e_remove use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.2/6.19-rc1. It has been rated as critical. Affected is the function _mlx5e_remove in the library lib/refcount.c of the component refcount_t. This manipulation causes use after free. The identification of this vulnerability is CVE-2025-68779. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.18.2/6.19-rc1. Affected by this vulnerability is the function _mlx5e_remove in the library lib/refcount.c of the component refcount_t. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. 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/mlx5e: Avoid unregistering PSP twice PSP is unregistered twice in: _mlx5e_remove -> mlx5e_psp_unregister mlx5e_nic_cleanup -> mlx5e_psp_unregister This leads to a refcount underflow in some conditions: ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 2 PID: 1694 at lib/refcount.c:28 refcount_warn_saturate+0xd8/0xe0 [...] mlx5e_psp_unregister+0x26/0x50 [mlx5_core] mlx5e_nic_cleanup+0x26/0x90 [mlx5_core] mlx5e_remove+0xe6/0x1f0 [mlx5_core] auxiliary_bus_remove+0x18/0x30 device_release_driver_internal+0x194/0x1f0 bus_remove_device+0xc6/0x130 device_del+0x159/0x3c0 mlx5_rescan_drivers_locked+0xbc/0x2a0 [mlx5_core] [...] Do not directly remove psp from the _mlx5e_remove path, the PSP cleanup happens as part of profile cleanup.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2025-68779 since 12/24/2025. The exploitation appears to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 03/27/2026).

Upgrading to version 6.18.3 or 6.19-rc2 eliminates this vulnerability. Applying the patch e12c912f92ccea671b514caf371f28485714bb4b/35e93736f69963337912594eb3951ab320b77521 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 vulnerability database at CERT Bund (WID-SEC-2026-0086). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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

• 6.18.0
• 6.18.1
• 6.18.2
• 6.19-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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