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CVE-2026-53373
mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap()
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem include/linux. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53373 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 | 7.0.9-1 | Update the kernel and reboot. Fixed in 7.0.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.9-1 | Update the kernel and reboot. Fixed in 7.0.9-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The mmap_prepare hook functionality includes the ability to invoke mmap_prepare() from the mmap() hook of existing 'stacked' drivers, that is ones which are capable of calling the mmap hooks of other drivers/file systems (e.g. overlayfs, shm). As part of the mmap_prepare action functionality, we deal with errors by unmapping the VMA should one arise. This works in the usual mmap_prepare case, as we invoke this action at the last moment, when the VMA is established in the maple tree. However, the mmap() hook passes a not-fully-established VMA pointer to the caller (which is the motivation behind the mmap_prepare() work), which is detached. So attempting to unmap a VMA in this state will be problematic, with the most obvious symptom being a warning in vma_mark_detached(), because the VMA is already detached. It's also unncessary - the mmap() handler will clean up the VMA on error. So to fix this issue, this patch propagates whether or not an mmap action is being completed via the compatibility layer or directly. If the former, then we do not attempt VMA cleanup, if the latter, then we do. This patch also updates the userland VMA tests to reflect the change.
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/mm.h
mm/util.c
mm/vma.c
tools/testing/vma/include/dup.h
tools/testing/vma/include/stubs.h
- What this is
- MEMORY MANAGEMENT - COREMAINTAINERS section matched on include/linux/mm.h · 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
- 2026-07-19 (3 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 5.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.19 | 7.0.9 | 5394bcb74650 |
| 6.19 | 7.1 | 619eab23e1ce |
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 vulnerability is reached only through the mmap/mmap2 syscall path (ksys_mmap_pgoff → do_mmap → mmap_region → __mmap_region → stacked .mmap() → compat_vma_mmap → mmap_action_complete), which requires local process access to invoke the kernel memory-management interface.
- AC:LAttack complexity, low
- An attacker fully controls mmap parameters (address, length, fd, flags) and can create overlapping mappings to place detached VMAs in the target range before triggering a stacked mmap_prepare action failure, making exploitation conditions attacker-influenced rather than dependent on rare external timing or layout.
- PR:LPrivileges required, low
- Triggering requires only the ability to call mmap() on an open file descriptor; syzbot reported this from unprivileged fuzzing, and stacked paths (overlayfs, shm, fuse passthrough) are reachable by ordinary local users who can open/mmap files in their mount namespace without real init-namespace root.
- UI:NUser interaction, none
- Exploitation requires no victim interaction beyond the attacker's own mmap syscall; no third-party user action such as opening a file or mounting a filesystem on behalf of the attacker is needed.
- S:UScope, unchanged
- The flawed cleanup corrupts the calling process's own mm_struct/VMA state within the kernel; it does not by itself cross a security boundary such as guest-to-host VM escape or an IOMMU/DMA sandbox bypass.
- C:HConfidentiality impact, high
- Erroneous do_munmap() on VMAs that are detached but still linked in the maple tree during an in-progress mmap corrupts kernel memory-management metadata, which is a memory-corruption primitive that can be leveraged for arbitrary kernel memory disclosure, not merely a benign warning.
- I:HIntegrity impact, high
- The double-unmap/detach of VMAs in a transitional mmap state can leave the address-space tree inconsistent and is a memory-corruption bug in kernel structures that could be developed into arbitrary write or privilege-escalation primitives, not limited to integrity-neutral denial of service.
- A:HAvailability impact, high
- The known symptom is a WARN in vma_mark_detached() on already-detached VMAs, and operating on refcount-zero detached VMAs during a nested unmap can provoke kernel oops/panic or leave the mm in a crash-prone inconsistent state, satisfying high availability impact.