# CVE-2026-74619: ovl: don't warn when the mount is completed from another user namespace

> An unprivileged local user can trigger a kernel warning loop in the overlayfs module, potentially causing a denial of service or kernel panic.

- **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:** 22 Aug 2026
- **Updated:** 22 Aug 2026
- **Also known as:** AZL-97122, BELL-CVE-2026-74619, DEBIAN-CVE-2026-74619, GHSA-j34r-65f7-8j2q, UBUNTU-CVE-2026-74619

## What is CVE-2026-74619?

CVE-2026-74619 is a denial of service vulnerability in Linux, published on 22 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:

ovl: don't warn when the mount is completed from another user namespace

fsopen() records the caller's user namespace in fc->user_ns and hands
back an ordinary file descriptor. Nothing ties the task that calls
fsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The
fd is inherited across fork() and exec() and it can be passed over a
unix socket.

Completing a context from another user namespace is allowed on purpose.
vfs_cmd_create() authorizes the create with mount_capable(), which for
FS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that
succeeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns.
So an unprivileged task can reach the WARN_ON() in ovl_fill_super():
create a user and a mount namespace in a child, call fsopen("overlay")
there, send the fscontext fd to the parent and let the parent issue
FSCONFIG_CMD_CREATE. Both namespaces come from a plain unshare(1) and no
capability is needed anywhere:

  WARNING: fs/overlayfs/super.c:1551 at ovl_fill_super+0x7b9/0x1e20 [overlay]
  CPU: 3 UID: 1000 PID: 3243376 Comm: fswarn
  Call Trace:
   get_tree_nodev+0x71/0xa0
   ovl_get_tree+0x15/0x20 [overlay]
   vfs_get_tree+0x2a/0x100
   vfs_cmd_create+0x60/0xf0
   __do_sys_fsconfig+0x4b2/0x500

The child needs the mount namespace because fsopen() itself gates on
may_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning
the caller's mount namespace. fsconfig() doesn't repeat that check.

It is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be
raised in a loop to taint the kernel and flood the log, and it panics a
kernel booted with panic_on_warn.

Keep refusing the mount and stop warning about it. ovl_parse_param()
already spells a user namespace check this way for Opt_override_creds.

## Which versions are affected by CVE-2026-74619?


## How do I fix CVE-2026-74619?

Apply the vendor's patch.

## Is CVE-2026-74619 being exploited?

There is no known exploitation of CVE-2026-74619 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74619 and fix it if it is affected.

What it is: CVE-2026-74619 is a denial of service vulnerability in Linux, published on 22 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-2026-74619 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-2026-74619/ (Markdown: https://insights.sbomify.com/CVE-2026-74619/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74619
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74619
- OSV: https://osv.dev/vulnerability/CVE-2026-74619

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74619/
Summaries are generated and may contain mistakes; the official description above is the record.