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CVE-2026-89988
kprobes: Protect kprobe_blacklist with RCU
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem include/linux. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89988 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 | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
__within_kprobe_blacklist() traverses kprobe_blacklist without holding kprobe_mutex. When a module is unloaded, kprobe_remove_area_blacklist() removes blacklist entries and immediately frees them with kfree(). A concurrent call to within_kprobe_blacklist() can therefore dereference freed memory. Furthermore, within_kprobe_blacklist() can be called in atomic or non-preemptible contexts where the sleeping kprobe_mutex cannot be taken. Protect kprobe_blacklist with RCU. Use guard(rcu)() and list_for_each_entry_rcu() for traversal, list_add_tail_rcu() for insertions, list_del_rcu() for deletions, and kfree_rcu() to reclaim entries safely after a grace period.
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.
include/linux/kprobes.h
kernel/kprobes.c
- What this is
- KPROBESMAINTAINERS section matched on include/linux/kprobes.h · linux-kernel@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_KPROBES /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 code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_KPROBES
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
- 2026-09-16 (33 days 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
- not yet assignedsource
- Subsystem
- include/linux
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.16 | 6.1.188 | 8f406205003f |
| 3.16 | 6.6.157 | 630ed8734a02 |
| 3.16 | 6.12.110 | 518d9b5568bb |
| 3.16 | 6.18.51 | 5da247e4d1e8 |
| 3.16 | 7.2.5 | 6e62cf983a2b |
| 3.16 | 7.3 | 0c4256196b3a |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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 UAF is reached only via local syscalls: x86 perf_event_open() hardware execute breakpoints and register_kprobe() (tracefs, perf kprobes, BPF). It is not invoked from network packet processing or a remote service.
- AC:LAttack complexity, low
- An attacker can loop the blacklist walk while concurrently causing module COMING/GOING so kprobe_remove_area_blacklist() does list_del/kfree, creating both sides of the race. Attacker-driven use-after-free races are AC:L.
- PR:LPrivileges required, low
- x86 hw_breakpoint_arch_parse() calls within_kprobe_blacklist() for kernel execute breakpoints during perf_event_open() before hw_breakpoint_parse()'s CAP_SYS_ADMIN check, so an unprivileged user can trigger the walk. Module autoload via request_module() can mutate the list without CAP_SYS_MODULE.
- UI:NUser interaction, none
- The attacker triggers the race with their own syscalls (perf_event_open and module autoload/unload). No separate victim action is required.
- S:UScope, unchanged
- The bug is kernel-heap use-after-free in kprobes. Effects stay inside the kernel's security authority and do not cross a VM, IOMMU, or other boundary.
- C:HConfidentiality impact, high
- Concurrent walk versus kfree of struct kprobe_blacklist_entry is a heap use-after-free. Reclaiming the object yields an arbitrary kernel read primitive, so confidentiality impact is high.
- I:HIntegrity impact, high
- A heap use-after-free on a list node is exploitable via heap spraying for an arbitrary write and control-flow hijack, so integrity impact is high.
- A:HAvailability impact, high
- Following the freed blacklist entry's next pointer or fields causes a kernel oops or panic, taking down the system.