# CVE-2026-74477: uprobes: Fix NULL pointer dereference in hprobe_expire()

> A local attacker can trigger a kernel crash by forking a task with a pending uretprobe, causing a NULL pointer dereference in the Linux kernel.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-74477, DEBIAN-CVE-2026-74477, GHSA-pgww-xqqj-6xv5, UBUNTU-CVE-2026-74477

## What is CVE-2026-74477?

CVE-2026-74477 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

uprobes: Fix NULL pointer dereference in hprobe_expire()

Forking a task that has a pending uretprobe can oops the kernel with a
NULL pointer dereference in the clone() path:

  BUG: kernel NULL pointer dereference, address: 0000000000000018
  Oops: 0002 [#1] SMP NOPTI
  RIP: 0010:hprobe_expire
  CR2: 0000000000000018
  Call Trace:
   uprobe_copy_process
   copy_process
   kernel_clone
   __x64_sys_clone
   do_syscall_64
   entry_SYSCALL_64_after_hwframe

This was found on real hosts on Meta fleet.

I've got the impression that this is what is happening:

  CPU 1                          CPU 2 (traced task)
  -----                          -------------------
                                 hit uprobe, prepare_uretprobe():
                                   hprobe LEASED, refcount >= 1
  uprobe_unregister()
    put_uprobe(): refcount -> 0
                                 fork() -> dup_utask()
                                   hprobe_expire(hprobe, true)
                                     try_get_uprobe() -> NULL
                                     get_uprobe(NULL)   <-- Oops

Only take the extra reference when the uprobe is non-NULL; a NULL means
it is gone and is the correct value to return.

## Which versions are affected by CVE-2026-74477?


## How do I fix CVE-2026-74477?

Apply the vendor's patch.

## Is CVE-2026-74477 being exploited?

There is no known exploitation of CVE-2026-74477 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74477 and fix it if it is affected.

What it is: CVE-2026-74477 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74477 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74477/ (Markdown: https://insights.sbomify.com/CVE-2026-74477/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74477
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74477
- OSV: https://osv.dev/vulnerability/CVE-2026-74477

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74477/
Summaries are generated and may contain mistakes; the official description above is the record.