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CVE-2026-72080
fs/resctrl: Fix use-after-free during unmount
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/resctrl. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72080 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
During unmount or failure teardown all mon_data structures that contain monitoring event file private data are freed after which kernfs nodes are removed. However, the RDT_DELETED flag is never set for the statically allocated default resource group. A concurrent reader of an event file associated with the default resource group may, after dropping kernfs active protection, block on rdtgroup_mutex while unmount proceeds to free the file private data and destroy the kernfs node without waiting for the reader. When the mutex is released, the reader wakes up, observes that RDT_DELETED is not set for the default group, and dereferences the already-freed file private data. The scenario can be depicted as follows: CPU0 CPU1 /* * Default resource group's * monitoring data accessible via * kernfs file with kernfs_node::priv * pointing to a struct mon_data. * User opens the file for reading. */ rdtgroup_mondata_show() /* arch encounters fatal error */ rdtgroup_kn_lock_live() resctrl_exit() atomic_inc(&rdtgroup_default.waitcount) cpus_read_lock() kernfs_break_active_protection(kn) mutex_lock(&rdtgroup_mutex) cpus_read_lock() resctrl_fs_teardown() mutex_lock(&rdtgroup_mutex) rmdir_all_sub() mon_put_kn_priv() /* Delete all mon_data structures */ rdtgroup_destroy_root() kernfs_destroy_root() rdtgroup_default.kn = NULL mutex_unlock(&rdtgroup_mutex) /* * rdtgroup_default.flags is empty so * rdtgroup_kn_lock_live() returns * &rdtgroup_default */ md = of->kn->priv; /* md points to freed mon_data */ Set RDT_DELETED for the default group unconditionally since the flag does not lead to the freeing of this statically allocated group. Do not allow a new resctrl mount if there are any waiters on default group of previous mount. A new mount will re-initialize the default group that would appear to waiters from previous mount as though the default group is accessible causing them to access the mon_data structures from the previous mount that have been removed.
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.
fs/resctrl/rdtgroup.c
- What this is
- RDT - RESOURCE ALLOCATIONMAINTAINERS section matched on fs/resctrl/ · linux-kernel@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_RESCTRL_FS /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. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidYnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- Y
- built in where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_RESCTRL_FS
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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/resctrl
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.16 | 6.18.42 | 7b7bb07efe41 |
| 6.16 | 7.1.5 | 7d330a1d6633 |
| 6.16 | 7.2 | 52fce648607e |
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 bug is reached by a local process reading resctrl monitoring event files under /sys/fs/resctrl via open/read on kernfs; there is no network, Bluetooth, or physical-device entry path to rdtgroup_mondata_show().
- AC:LAttack complexity, low
- This is a race between a reader in rdtgroup_kn_lock_live() and teardown in resctrl_fs_teardown()/resctrl_exit(); an attacker can drive both sides with concurrent threads (read mondata while unmounting or during MPAM-initiated teardown) and retry until the window is hit.
- PR:LPrivileges required, low
- Default-group mondata files are world-readable (0444) once resctrl is mounted; triggering teardown via umount is reachable with CAP_SYS_ADMIN from an unprivileged user namespace, and on ARM MPAM systems resctrl_exit() can run while any local user is reading.
- UI:NUser interaction, none
- No victim interaction is required; the attacker opens and reads monitoring files and initiates or times concurrent resctrl unmount/teardown themselves to win the race.
- S:UScope, unchanged
- Exploitation corrupts kernel heap memory and enables local privilege escalation within the same kernel security authority; it does not cross a VM, container, or IOMMU boundary by itself.
- C:HConfidentiality impact, high
- Use-after-free of kmalloc'd struct mon_data lets the attacker influence freed object contents; subsequent reads of md->rid, md->domid, and md->evt enable arbitrary kernel memory disclosure through mon_event_read().
- I:HIntegrity impact, high
- The UAF provides a controllable heap primitive; forged mon_data/evt pointers passed into mon_event_read() and resctrl_arch_mon_ctx_alloc() can be leveraged for arbitrary kernel writes and local code execution.
- A:HAvailability impact, high
- Dereferencing freed mon_data during rdtgroup_mondata_show() can immediately kernel oops/panic the system, and repeated triggering of the race provides a reliable denial-of-service even before full exploitation.