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medium 5.5

CVE-2025-21834 json

seccomp: passthrough uretprobe systemcall without filtering

published last yr. modified 4mo ago also EUVD-2025-6211

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

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]

Patch / fix

  • Linux Linux 6.12.14, 6.13.3, 6.14
  • linux Debian 14, Debian 13 6.12.15-1

debian advisories DEBIAN-CVE-2025-21834

  • linux-hwe-6.11 Ubuntu 24.04 LTS 6.11.0-21.21~24.04.1
  • linux-oem-6.11 Ubuntu 24.04 LTS 6.11.0-1017.17

ubuntu advisories UBUNTU-CVE-2025-21834

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 10.2 6.12.0-211.50.1.el10_2
  • rv RHEL 10.2 6.12.0-211.50.1.el10_2
  • perf RHEL 10.2 6.12.0-211.50.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.50.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.50.1.el10_2

red hat advisories RHSA-2026:61887

  • kernel AlmaLinux 10 6.12.0-211.50.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.50.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.50.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.50.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.50.1.el10_2

almalinux advisories ALSA-2026:61887

  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2

rocky linux advisories RLSA-2026:61887

Is CVE-2025-21834 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-21834 updated cvss 5.5

kernel: seccomp: passthrough uretprobe systemcall without filtering

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2 Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.