CVE-2026-64031 erofs: fix managed cache race for unaligned extents
A race condition in the Linux kernel's EROFS filesystem can cause a denial of service when handling unaligned compressed extents.
- 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-2026-64031?
CVE-2026-64031 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:
erofs: fix managed cache race for unaligned extents
After unaligned compressed extents were introduced, the following race could occur:
[Thread 1] [Thread 2] (z_erofs_fill_bio_vec) <handle a Z_EROFS_PREALLOCATED_FOLIO folio> ... filemap_add_folio (1) (z_erofs_bind_cache) <the same folio is found..> .. .. folio_attach_private (2) filemap_add_folio (3) again
Since (1) is executed but (2) hasn't been executed yet, it's possible that another thread finds the same managed folio in z_erofs_bind_cache() for a different pcluster and calls filemap_add_folio() again since folio->private is still Z_EROFS_PREALLOCATED_FOLIO.
Fix this by explicitly clearing folio->private before making the folio visible in the managed cache so that another pcluster can simply wait on the locked managed folio as what we did for other shared cases [1].
This only impacts unaligned data compression (`-E48bit` with zstd, for example).
[1] Commit 9e2f9d34dd12 ("erofs: handle overlapped pclusters out of crafted images properly") was originally introduced to handle crafted overlapped extents, but it addresses unaligned extents as well.
Weakness: CWE-362
Which versions are affected by CVE-2026-64031?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64031?
Apply the vendor's patch.
Is CVE-2026-64031 being exploited?
There is no known exploitation of CVE-2026-64031 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64031, DEBIAN-CVE-2026-64031, GHSA-22cv-hg25-xph5, UBUNTU-CVE-2026-64031.