# CVE-2026-89766: pidfd: hold exec_update_lock around namespace ioctl

> A race condition in Linux kernel pidfd namespace ioctls allows local attackers to bypass ptrace access checks and read restricted namespace information.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89766, DEBIAN-CVE-2026-89766, GHSA-7f3v-362v-5m4g, UBUNTU-CVE-2026-89766

## What is CVE-2026-89766?

CVE-2026-89766 is a vulnerability in Linux, published on 11 Sep 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:

pidfd: hold exec_update_lock around namespace ioctl

The PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem
credentials ptrace access check before handing out a namespace file
descriptor.  The accompanying comment states that the code "mirrors nsfs
behavior", but, unlike the corresponding procfs paths, it does so without
holding the target task's exec_update_lock.

proc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for
reading around the ptrace check and the namespace lookup, so that the
credentials used for the access decision match those of the task when its
namespace is read.  Without it, a caller can pass the check against the
target's old credentials and then read the namespace after the target has
execve()'d a setuid binary and committed new credentials -- accessing
namespace information it should have been denied.

Hold exec_update_lock for reading around the ptrace check and the
namespace lookup so that pidfd truly mirrors nsfs behavior, as the comment
already claims.  open_namespace() itself runs outside the lock: once a
namespace reference is obtained it carries its own refcount and is opened
with the caller's own credentials, so a concurrent execve() on the target
can no longer affect the outcome.

## Which versions are affected by CVE-2026-89766?


## How do I fix CVE-2026-89766?

Apply the vendor's patch.

## Is CVE-2026-89766 being exploited?

There is no known exploitation of CVE-2026-89766 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89766 and fix it if it is affected.

What it is: CVE-2026-89766 is a vulnerability in Linux, published on 11 Sep 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-2026-89766 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-2026-89766/ (Markdown: https://insights.sbomify.com/CVE-2026-89766/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89766
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89766
- OSV: https://osv.dev/vulnerability/CVE-2026-89766

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89766/
Summaries are generated and may contain mistakes; the official description above is the record.