CVE-2026-52956

In the Linux kernel, the following vulnerability has been resolved:

libceph: Fix potential out-of-bounds access in __ceph_x_decrypt()

In __ceph_x_decrypt(), a part of the buffer p is interpreted as a

ceph_x_encrypt_header, and the magic field of this struct is accessed.

This happens without any guarantee that the buffer is large enough to

hold this struct. The function parameter ciphertext_len represents the

length of the ciphertext to decrypt and is guaranteed to be at most the

remaining size of the allocated buffer p. However, this value is not

necessarily greater than sizeof(ceph_x_encrypt_header). E.g., a message

frame of type FRAME_TAG_AUTH_REPLY_MORE, that is just as long to hold

the ciphertext at its end with a ciphertext_len of 8 or less, can

trigger an out-of-bounds memory access when accessing hdr->magic.

This patch fixes the issue by adding a check to ensure that the

decrypted plaintext in the buffer is large enough to represent at least

the ceph_x_encrypt_header.