CVE-2026-68148
In the Linux kernel, the following vulnerability has been resolved: fscrypt: Add missing superblock check in find_or_insert_direct_key() The legacy 'fscrypt_direct_keys' table caches master keys that are used by v1 encryption policies that have…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.09%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: fscrypt: Add missing superblock check in find_or_insert_direct_key() The legacy 'fscrypt_direct_keys' table caches master keys that are used by v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY. It's just a global table for all filesystems (since the keys can be provided by the legacy process-subscribed keyrings mechanism, which makes it difficult to reuse super_block::s_master_keys). The entries in it ('struct fscrypt_direct_key') do contain a super_block pointer, though, for passing to fscrypt_destroy_inline_crypt_key() when the last inode that references the key is evicted. However, when finding the fscrypt_direct_key for an inode, we weren't actually comparing the super_block pointer. As a result, inodes with different super_blocks could point to the same fscrypt_direct_key. That could extend the lifetime of a fscrypt_direct_key beyond the super_block it points to, causing a use-after-free later. Fix this by creating distinct fscrypt_direct_key structs for distinct super_block structs. Note that this problem doesn't exist in the v2 policy equivalent ("per-mode keys"), since the data structures there are per super_block.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.09% probability · 1th percentile
- CISA KEV
- Not listed
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/330249609b70778094a7a36f5b6bcfa6362121d4
- https://git.kernel.org/stable/c/466f187b501a5ac8e1ea2ccf3ccd5c46108d8830
- https://git.kernel.org/stable/c/95376fe9c145be35566991df99c53134943d992f
- https://git.kernel.org/stable/c/965b5bc8cf5031225e057979ce660fec2bd5fbfc
- https://git.kernel.org/stable/c/b5fa40226e71c17847b9ff2816c6ca4133d0d994
- https://git.kernel.org/stable/c/deff41898a5ae3a47db5fa1896a494aa95efda5d
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.