Medium [CVE-2026-68433] bound get_version reply decode to front len

In the Linux kernel, the following vulnerability has been resolved: libceph: bound get_version reply decode to front len handle_get_version_reply() uses msg->front_alloc_len as the decode boundary for MON_GET_VERSION_REPLY. That is the size of the reused reply buffer, not the number of bytes actually received.

A truncated reply can therefore pass ceph_decode_need() and decode the second u64 from stale tail bytes left in the buffer by an earlier message, causing an uninitialized memory read. Use msg->front.iov_len as the receive-side decode boundary, matching other libceph reply handlers and limiting decoding to the bytes that were actually read from the wire.

This vulnerability occurs because the system incorrectly processes replies, using an allocated buffer size rather than the actual received data length. A specially crafted, truncated reply can lead to the system reading uninitialized memory.

This could result in the disclosure of sensitive information or cause system instability. This issue affects systems using the in-kernel Ceph client (libceph).

MON_GET_VERSION_REPLY decoding used the allocated buffer size instead of received length, allowing stale tail bytes to be read on truncated replies from the monitor. Systems without Ceph are not affected.

Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-125.