CVE-2026-53373 mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap()
A kernel bug causes a warning and potential instability when unmapping a detached VMA during mmap operations in stacked drivers.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53373?
CVE-2026-53373 is a high-severity vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap()
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.
Which versions are affected by CVE-2026-53373?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53373?
Apply the vendor's patch.
Is CVE-2026-53373 being exploited?
There is no known exploitation of CVE-2026-53373 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2026-53373, GHSA-vfrx-cq74-4pr7, UBUNTU-CVE-2026-53373.