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CVE-2026-72027
mm/compaction: handle free_pages_prepare() properly in compaction_free()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem mm. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72027 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 | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| 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
free_pages_prepare() can fail but compaction_free() does not handle the failure case. Failed pages should not be added back to cc->freepages for future use, since they can be either PageHWPoison or free_page_is_bad() and might cause data corruption.
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/compaction.c
- What this is
- MEMORY MANAGEMENT - PAGE ALLOCATORMAINTAINERS section matched on mm/compaction.c · linux-mm@kvack.org · Maintained
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, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
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 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
- 0.18%, higher than 6.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- mm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.9 | 6.12.97 | de8577db0903 |
| 6.9 | 6.18.40 | 018d7ad26cb8 |
| 6.9 | 7.1.5 | 23afc3786acf |
| 6.9 | 7.2 | 7da7d599b8a8 |
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 in mm/compaction.c compaction_free(), reached only via local kernel memory-management paths (__alloc_pages_slowpath/try_to_compact_pages, kcompactd, or root sysctl), not from network packet handlers or physical device insertion.
- AC:LAttack complexity, low
- An unprivileged attacker can reliably drive compaction (THP/high-order mmap, memory pressure) and concurrently force migrate_pages failures and races so compaction_free() runs on pages where free_pages_prepare() rejects them; both sides are attacker-influenceable.
- PR:LPrivileges required, low
- No special capability is required: ordinary local processes trigger direct compaction through normal allocators and transparent hugepage mappings, and user namespaces do not block these memory syscalls or kcompactd-driven compaction on the host.
- UI:NUser interaction, none
- Exploitation requires only the attacker's own memory-allocation and churn activity; no separate victim must mount filesystems, open files, or perform other interactive steps beyond routine process execution.
- S:UScope, unchanged
- Recycling PageHWPoison or free_page_is_bad() pages corrupts host kernel page-allocator/compaction state and process memory within the same OS security authority, not a VM-guest-to-host or IOMMU boundary crossing.
- C:HConfidentiality impact, high
- Reusing pages that failed free_pages_prepare() can expose stale kernel or cross-process contents and enables allocator/page aliasing primitives; under the overestimate rule, this memory-corruption class supports high confidentiality impact.
- I:HIntegrity impact, high
- The fix explicitly warns these pages may cause data corruption when returned to cc->freepages; compaction_alloc() later hands them to migrate_pages as destinations, allowing corrupted/compound state to be written into live mappings.
- A:HAvailability impact, high
- Reallocating HWPoison or allocator-marked bad pages during compaction can trigger kernel faults, bad-page detection, oopses, or panics when the poisoned folio is touched, satisfying high availability impact under the kernel crash guidance.