CVE-2025-21834: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: seccomp: passthrough uretprobe systemcall without filtering When attaching uretprobes to processes running inside docker, the attached process is segfaulted when encountering the retprobe. The reason is that now that uretprobe is a system call the default seccomp filters in docker block it as they only allow a specific set of known syscalls. This is true for other userspace applications which use seccomp to control their syscall surface. Since uretprobe is a "kernel implementation detail" system call which is not used by userspace application code directly, it is impractical and there's very little point in forcing all userspace applications to explicitly allow it in order to avoid crashing tracked processes. Pass this systemcall through seccomp without depending on configuration. Note: uretprobe is currently only x86_64 and isn't expected to ever be supported in i386. [kees: minimized changes for easier backporting, tweaked commit log]

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.11 — 6.12.14
linux	linux_kernel	6.13 — 6.13.3
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/5a262628f4cf2437d863fe41f9d427177b87664c https://git.kernel.org/stable/c/cf6cb56ef24410fb5308f9655087f1eddf4452e6 https://git.kernel.org/stable/c/fa80018aa5be10c35e9fa896b7b4061a8dce3eed

Frequently Asked Questions

What is CVE-2025-21834? +

In the Linux kernel, the following vulnerability has been resolved: seccomp: passthrough uretprobe systemcall without filtering When attaching uretprobes to processes running inside docker, the attached process is segfaulted when encountering the retprobe. The reason is that now that uretprobe is a system call the default seccomp filters in docker block it as they only allow a specific set of known syscalls. This is true for other userspace applications which use seccomp to control their syscall surface. Since uretprobe is a "kernel implementation detail" system call which is not used by userspace application code directly, it is impractical and there's very little point in forcing all userspace applications to explicitly allow it in order to avoid crashing tracked processes. Pass this systemcall through seccomp without depending on configuration. Note: uretprobe is currently only x86_64 and isn't expected to ever be supported in i386. [kees: minimized changes for easier backporting, tweaked commit log] It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21834? +

CVE-2025-21834 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21834? +

CVE-2025-21834 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21834? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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