CVE-2025-40241 erofs: fix crafted invalid cases for encoded extents
Crafted EROFS filesystem images can cause system crashes via out-of-bound access in the Linux kernel, requiring a patch to prevent denial of service.
- 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-2025-40241?
CVE-2025-40241 is a high-severity denial of service vulnerability in Linux, published on 4 Dec 2025. 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 crafted invalid cases for encoded extents
Robert recently reported two corrupted images that can cause system crashes, which are related to the new encoded extents introduced in Linux 6.15:
- The first one [1] has plen != 0 (e.g. plen == 0x2000000) but (plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent special extents such as sparse extents (!EROFS_MAP_MAPPED), but previously only plen == 0 was handled;
- The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000, then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in "} while ((cur += bvec.bv_len) < end);" wraps around, causing an out-of-bound access of pcl->compressed_bvecs[] in z_erofs_submit_queue(). EROFS only supports 48-bit physical block addresses (up to 1EiB for 4k blocks), so add a sanity check to enforce this.
Which versions are affected by CVE-2025-40241?
How do I fix CVE-2025-40241?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-40241 being exploited?
There is no known exploitation of CVE-2025-40241 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40241, DEBIAN-CVE-2025-40241, GHSA-9f7m-pc72-73fj, UBUNTU-CVE-2025-40241.