Use-after-free in Linux kernel - CVE-2025-21786

Vulnerability identifier: #VU104951

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2025-21786

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error within the send_mayday() and worker_detach_from_pool() functions in kernel/workqueue.c. A local user can escalate privileges on the system.

Linux kernel
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Ubuntu
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
kernel (Red Hat package)
linux (Ubuntu package)
linux-gke (Ubuntu package)
linux-aws-6.8 (Ubuntu package)
linux-azure (Ubuntu package)
linux-oracle (Ubuntu package)
linux-raspi-realtime (Ubuntu package)
linux-aws (Ubuntu package)
linux-lowlatency (Ubuntu package)

Install update from vendor's website.

Linux kernel - update to 6.12.16
kernel (Red Hat package) - update to 5.14.0-570.86.1.el9_6
linux (Ubuntu package) - addressed in versions 6.8.0-78.78, 6.8.0-78.78.1, 6.8.0-78.78.1~22.04.1, 6.8.0-1035.37, 6.8.1-1030.31, 6.11.0-26.26, 6.11.0-26.26~24.04.1, 6.11.0-1010.10, 6.11.0-1013.13, 6.11.0-1015.15, 6.11.0-1015.15~24.04.1, 6.11.0-1022.22
linux-gke (Ubuntu package) - addressed in versions 6.8.0-78.78~22.04.1, 6.8.0-1032.36, 6.8.0-1035.38, 6.8.0-1035.38.1, 6.8.0-1035.38~22.04.1, 6.8.0-1035.39
linux-aws-6.8 (Ubuntu package) - addressed in versions 6.8.0-1019.21~22.04.1, 6.8.0-1033.33, 6.8.0-1033.33~22.04.1, 6.8.0-1035.37~22.04.1, 6.8.0-1036.38, 6.8.0-1036.38~22.04.1
linux-azure (Ubuntu package) - addressed in versions 6.8.0-1022.23, 6.8.0-1034.39, 6.8.0-1034.39~22.04.1
linux-oracle (Ubuntu package) - update to 6.8.0-1032.33~22.04.1
linux-raspi-realtime (Ubuntu package) - update to 6.8.0-2028.29
linux-aws (Ubuntu package) - update to 6.11.0-1014.15
linux-lowlatency (Ubuntu package) - addressed in versions 6.11.0-1014.15, 6.11.0-1014.15~24.04.1, 6.11.0-1016.17

• https://git.kernel.org/stable/c/835b69c868f53f959d4986bbecd561ba6f38e492
• https://git.kernel.org/stable/c/e76946110137703c16423baf6ee177b751a34b7e
• https://git.kernel.org/stable/c/e7c16028a424dd35be1064a68fa318be4359310f
• https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.12.16

• Use-after-free in Linux kernel
• Ubuntu update for linux
• Ubuntu update for linux-aws
• Ubuntu update for linux-lowlatency
• Ubuntu update for linux
• Ubuntu update for linux-aws-6.8
• Ubuntu update for linux-oracle
• Ubuntu update for linux-raspi-realtime
• Ubuntu update for linux-gke
• Ubuntu update for linux-azure
• Red Hat Enterprise Linux 9 update for kernel