# CVE-2026-43408: ceph: add a bunch of missing ceph_path_info initializers

> Missing initializers in Ceph kernel code cause crashes and potential privilege escalation when freeing uninitialized path info structures.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 8 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-43408, DEBIAN-CVE-2026-43408, GHSA-97qv-cc94-mr6w, ROOT-OS-UBUNTU-2404-CVE-2026-43408, UBUNTU-CVE-2026-43408

## What is CVE-2026-43408?

CVE-2026-43408 is a high-severity vulnerability in Linux kernel, published on 8 May 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:

ceph: add a bunch of missing ceph_path_info initializers

ceph_mdsc_build_path() must be called with a zero-initialized
ceph_path_info parameter, or else the following
ceph_mdsc_free_path_info() may crash.

Example crash (on Linux 6.18.12):

  virt_to_cache: Object is not a Slab page!
  WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6732 kmem_cache_free+0x316/0x400
  [...]
  Call Trace:
   [...]
   ceph_open+0x13d/0x3e0
   do_dentry_open+0x134/0x480
   vfs_open+0x2a/0xe0
   path_openat+0x9a3/0x1160
  [...]
  cache_from_obj: Wrong slab cache. names_cache but object is from ceph_inode_info
  WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6746 kmem_cache_free+0x2dd/0x400
  [...]
  kernel BUG at mm/slub.c:634!
  Oops: invalid opcode: 0000 [#1] SMP NOPTI
  RIP: 0010:__slab_free+0x1a4/0x350

Some of the ceph_mdsc_build_path() callers had initializers, but
others had not, even though they were all added by commit 15f519e9f883
("ceph: fix race condition validating r_parent before applying state").
The ones without initializer are suspectible to random crashes.  (I can
imagine it could even be possible to exploit this bug to elevate
privileges.)

Unfortunately, these Ceph functions are undocumented and its semantics
can only be derived from the code.  I see that ceph_mdsc_build_path()
initializes the structure only on success, but not on error.

Calling ceph_mdsc_free_path_info() after a failed
ceph_mdsc_build_path() call does not even make sense, but that's what
all callers do, and for it to be safe, the structure must be
zero-initialized.  The least intrusive approach to fix this is
therefore to add initializers everywhere.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-457 (Use of Uninitialized Variable)

## Which versions are affected by CVE-2026-43408?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43408?

Apply the vendor's patch.

## Is CVE-2026-43408 being exploited?

There is no known exploitation of CVE-2026-43408 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43408 and fix it if it is affected.

What it is: CVE-2026-43408 is a high-severity vulnerability in Linux kernel, published on 8 May 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-2026-43408 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43408/ (Markdown: https://insights.sbomify.com/CVE-2026-43408/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43408
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43408
- OSV: https://osv.dev/vulnerability/CVE-2026-43408

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43408/
Summaries are generated and may contain mistakes; the official description above is the record.