# CVE-2026-93191: smack: fix incorrect task context in smack_msg_queue_msgrcv

> A flaw in the Linux kernel SMACK module allows unauthorized local users to read messages from System V message queues, bypassing Mandatory Access Control policies.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102807, BELL-CVE-2026-93191, DEBIAN-CVE-2026-93191, GHSA-9697-g343-86c8, UBUNTU-CVE-2026-93191

## What is CVE-2026-93191?

CVE-2026-93191 is a vulnerability in Linux, published on 17 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:

smack: fix incorrect task context in smack_msg_queue_msgrcv

The smack_msg_queue_msgrcv() function incorrectly checks
the permissions of the 'current' task instead of the
'target' task.

In the msgsnd() syscall path, if a receiver is already waiting,
the pipelined_send() optimization is used to push the message
directly to the receiver task:

    ipc/msg.c`pipelined_send():
    ` smp_store_release(&msr->r_msg, msg)

In this case, the 'sender' (current) task performs the check
on behalf of the 'receiver' task (msr->r_tsk, passed as the
'target' parameter):

  ipc/msg.c`pipelined_send():
  ` security_msg_queue_msgrcv(,, target := msr->r_tsk,,)

However, smack_msg_queue_msgrcv() ignores the 'target' and
checks 'current':

  smack_msg_queue_msgrcv(…)
  ` smk_curacc_msq(isp, MAY_READWRITE); // current task

'current' MAY satisfy smack_msg_queue_msgrcv r/w requirement,
but 'target' (the receiver task) might NOT;
as a result, an unauthorized receiver gets the message,
violating MAC policy.

Test:
1) create a sysv message queue with label “foo”
2) echo "bar foo r" >/smack/load2
3) msgrcv(,,,0,MSG_NOERROR) in "bar"-labeled task.
    The task is waiting for the messages ...
4) msgsnd() from a "foo"-labeled task:
"bar"-labeled task gets the message.

This patch fixes the issue by checking permission on the
'target' task instead of 'current'.

(2008-02-04, Casey Schaufler)

## Which versions are affected by CVE-2026-93191?


## How do I fix CVE-2026-93191?

Apply the vendor's patch.

## Is CVE-2026-93191 being exploited?

There is no known exploitation of CVE-2026-93191 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93191 and fix it if it is affected.

What it is: CVE-2026-93191 is a vulnerability in Linux, published on 17 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-2026-93191 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-2026-93191/ (Markdown: https://insights.sbomify.com/CVE-2026-93191/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93191
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93191
- OSV: https://osv.dev/vulnerability/CVE-2026-93191

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93191/
Summaries are generated and may contain mistakes; the official description above is the record.