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CVE-2026-53189
mm/huge_memory: update file PMD counter before folio_put()
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem mm. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53189 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
__split_huge_pmd_locked() updates the file/shmem RSS counter after dropping the PMD mapping's folio reference. If folio_put() drops the last reference, mm_counter_file() can later read freed folio state via folio_test_swapbacked(). Move the counter update before folio_put().
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.
mm/huge_memory.c
- What this is
- MEMORY MANAGEMENT - THP (TRANSPARENT HUGE PAGE)MAINTAINERS section matched on mm/huge_memory.c · linux-mm@kvack.org · Maintained
Check it on the machine
grep -w CONFIG_TRANSPARENT_HUGEPAGE /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.
- bookwormYnot built on amd64/rt/amd64, arm64/rt/arm64, armhf/armmp, armhf/rt/armmp, i386/rt/686-pae
- trixieYnot built on amd64/rt/amd64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/rt/armmp
- forky, sidYnot built on amd64/rt-amd64, arm64/rt-arm64, armhf/armmp
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_TRANSPARENT_HUGEPAGE
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
- 2026-06-25 (4 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
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- mm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.19 | 5.10.259 | 84b3212b166b |
| 4.19 | 5.15.210 | 108963978a68 |
| 4.19 | 6.1.176 | 459771c9cf30 |
| 4.19 | 6.6.143 | ae9d4caf6f13 |
| 4.19 | 6.12.94 | 6c29a8ba084e |
| 4.19 | 6.18.36 | 5f5b604e1e6b |
| 4.19 | 7.0.13 | ed5b03093129 |
| 4.19 | 7.1 | 8d878059924f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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
- Reachable by a local process through ordinary memory-management paths such as page fault creation of a file/shmem huge PMD followed by mprotect/munmap/mremap-style PMD splitting. No network, adjacent, or physical input path reaches this core MM helper.
- AC:LAttack complexity, low
- An attacker can create suitable file/shmem THP mappings and trigger PMD splits from their own process; any last-reference/race condition can be driven with attacker-controlled local threads and file operations. Under the uncertainty rule, this is Low complexity.
- PR:LPrivileges required, low
- The path requires only an unprivileged local user able to mmap and modify protections or mappings of their own file/tmpfs memory. No real root or init-namespace capability gate is required.
- UI:NUser interaction, none
- Exploitation does not require another user to take action. The local attacker can set up the mapping and trigger the split themselves.
- S:UScope, unchanged
- The vulnerable code is in the kernel MM subsystem and impacts kernel-managed resources within the same security authority. It is not a VM escape, IOMMU bypass, or cross-scope boundary violation.
- C:HConfidentiality impact, high
- The bug is a use-after-free read of folio state after the PMD mapping reference may be dropped. Following kernel UAF guidance and the higher-severity rule, this is treated as potentially enabling high confidentiality impact.
- I:HIntegrity impact, high
- The stale freed folio state controls which RSS counter is updated and represents UAF-driven kernel memory/accounting corruption in core MM. Following the UAF guidance and higher-severity rule, integrity impact is High.
- A:HAvailability impact, high
- A UAF in the huge PMD split path can corrupt kernel MM state and can plausibly lead to warnings, oopses, or crashes when repeatedly triggered. Kernel UAF availability impact is therefore High.