CVE-2026-93191

What the bug is

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)

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

security/smack/smack_lsm.c

What this is

SMACK SECURITY MODULEMAINTAINERS section matched on security/smack/ · linux-security-module@vger.kernel.org · Maintained

Kernel module

none to look for. The file would have gone into smack, and Debian does not compile it into that module, so finding smack in lsmod would say nothing about this CVE.

Check it on the machine

grep -w CONFIG_SECURITY_SMACK /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sid, bookworm · linux-6.12n

n

not enabled on any flavour - this release does not build the code

Build switch

CONFIG_SECURITY_SMACK

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-17 (31 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.20%, higher than 8.7% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

security/smack

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
2.6.25	5.10.270	4e49f997ef0c
2.6.25	5.15.221	dbece6c2f80b
2.6.25	6.1.188	7be4bd21c50a
2.6.25	6.6.157	ec47f4177046
2.6.25	6.12.110	e35dc5a4ed6d
2.6.25	6.18.52	c2ab27c2e115
2.6.25	7.2.6	d02c55e3ea82
2.6.25	7.3	fba3d32825f4

Debian advisories