# CVE-2026-68148: fscrypt: Add missing superblock check in find_or_insert_direct_key()

> A missing superblock check in the Linux kernel fscrypt module allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.

- **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:** 10 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-68148, DEBIAN-CVE-2026-68148, GHSA-r7wr-xw9j-768v, UBUNTU-CVE-2026-68148

## What is CVE-2026-68148?

CVE-2026-68148 is a high-severity use after free vulnerability in Linux, published on 10 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:

fscrypt: Add missing superblock check in find_or_insert_direct_key()

The legacy 'fscrypt_direct_keys' table caches master keys that are used
by v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY.
It's just a global table for all filesystems (since the keys can be
provided by the legacy process-subscribed keyrings mechanism, which
makes it difficult to reuse super_block::s_master_keys).

The entries in it ('struct fscrypt_direct_key') do contain a super_block
pointer, though, for passing to fscrypt_destroy_inline_crypt_key() when
the last inode that references the key is evicted.

However, when finding the fscrypt_direct_key for an inode, we weren't
actually comparing the super_block pointer.  As a result, inodes with
different super_blocks could point to the same fscrypt_direct_key.  That
could extend the lifetime of a fscrypt_direct_key beyond the
super_block it points to, causing a use-after-free later.

Fix this by creating distinct fscrypt_direct_key structs for distinct
super_block structs.

Note that this problem doesn't exist in the v2 policy equivalent
("per-mode keys"), since the data structures there are per super_block.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-68148?


## How do I fix CVE-2026-68148?

Apply the vendor's patch.

## Is CVE-2026-68148 being exploited?

There is no known exploitation of CVE-2026-68148 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68148 and fix it if it is affected.

What it is: CVE-2026-68148 is a high-severity use after free vulnerability in Linux, published on 10 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-2026-68148 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-2026-68148/ (Markdown: https://insights.sbomify.com/CVE-2026-68148/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68148
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68148
- OSV: https://osv.dev/vulnerability/CVE-2026-68148

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68148/
Summaries are generated and may contain mistakes; the official description above is the record.