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CVE-2026-46054
selinux: fix overlayfs mmap() and mprotect() access checks
Published 2026-05-27 (5 months ago) by the Linux kernel CNA. Subsystem security/selinux. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-46054 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6381-1 · 2026-07-05 · text | 6.12.95-1 | Update the kernel and reboot. DSA-6381-1 shipped the fix on 2026-07-05, in 6.12.95-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.4-1 | Update the kernel and reboot. Fixed in 7.0.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.4-1 | Update the kernel and reboot. Fixed in 7.0.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The existing SELinux security model for overlayfs is to allow access if the current task is able to access the top level file (the "user" file) and the mounter's credentials are sufficient to access the lower level file (the "backing" file). Unfortunately, the current code does not properly enforce these access controls for both mmap() and mprotect() operations on overlayfs filesystems. This patch makes use of the newly created security_mmap_backing_file() LSM hook to provide the missing backing file enforcement for mmap() operations, and leverages the backing file API and new LSM blob to provide the necessary information to properly enforce the mprotect() access controls.
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/selinux/hooks.c
security/selinux/include/objsec.h
- What this is
- SELINUX SECURITY MODULEMAINTAINERS section matched on security/selinux/ · selinux@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_SECURITY_SELINUX /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 builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixieYnot built on armel/rpi
- forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_SECURITY_SELINUX
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
- 2026-05-27 (5 months ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- security/selinux
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.19 | 6.6.144 | bc6c380c1159 |
| 4.19 | 6.12.95 | 8bacd09f12c2 |
| 4.19 | 6.18.38 | d84470219839 |
| 4.19 | 7.0.4 | cd0e707a927a |
| 4.19 | 7.1 | 82544d36b172 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6381-1 | 2026-07-05 | trixie 6.12.95-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The flaw is reached only via the local `mmap(2)`/`mprotect(2)` syscalls on a file residing on a stacked filesystem (overlayfs); there is no network-facing path.
- AC:LAttack complexity, low
- A confined process reliably triggers the missing backing-file check on every mmap/mprotect of an overlayfs file; there is no race, timing, or memory-layout condition outside the attacker's control.
- PR:LPrivileges required, low
- Exploitation requires a local, low-privileged (typically SELinux-confined) process; overlayfs is `FS_USERNS_MOUNT`, so even an unprivileged user can set up the overlay and reach these paths.
- UI:NUser interaction, none
- The attacking process performs mmap/mprotect itself; no action by any other user is needed.
- S:UScope, unchanged
- Both the vulnerable component (kernel/SELinux LSM) and the impacted resources (files governed by the same kernel/SELinux authority) lie within one security scope; there is no VM/IOMMU/hypervisor boundary crossing.
- C:HConfidentiality impact, high
- The missing backing-file check bypasses the mounter-credential `FILE__READ` gate, allowing a confined process to mmap and read the full contents of attacker-chosen backing files that SELinux policy was meant to protect.
- I:HIntegrity impact, high
- The bypass also defeats `FILE__WRITE`, `FILE__EXECUTE`, `PROCESS__EXECMEM`, and `FILE__EXECMOD` enforcement, letting a confined process modify shared-mapped backing files and execute code/modified content that policy explicitly forbids — a direct, serious integrity violation.
- A:NAvailability impact, none
- The defect is a missing permission check with no memory corruption, crash, hang, or resource exhaustion; availability is unaffected.