CVE-2026-52956: libceph: Fix potential out-of-bounds access in __ceph_x_decrypt()

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-10-30
Weakness: CWE-125

Description

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.

Affected products

Linux kernel: from 4.9.6 before 4.10; from 4.10 before 7.0.10; 7.1-rc1, 7.1-rc2, 7.1-rc3 — fixed in 4.10, 7.0.10
Linux: from 4.9.6 before 4.10 — fixed in 4.10

How to fix

Upgrade to a fixed version: Linux kernel 4.10, 7.0.10; Linux 4.10. Check the vendor advisory for mitigations.

References

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