CVE-2026-68433 in Linux
Summary
by MITRE • 08/12/2026
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.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability described represents a critical memory safety issue within the Linux kernel's Ceph storage client implementation specifically in the libceph library component. This flaw manifests as an uninitialized memory read condition that occurs during the processing of version reply messages from Ceph monitors. The vulnerability is particularly concerning because it involves the improper handling of message boundaries during network protocol decoding, creating a potential vector for information disclosure or system instability.
The technical root cause stems from a mismatch between the buffer size used for decoding and the actual data received over the network. In the handle_get_version_reply() function, the code incorrectly utilizes msg->front_alloc_len as the decode boundary for MON_GET_VERSION_REPLY messages. This parameter represents the allocated size of the reusable reply buffer rather than the actual number of bytes that were successfully received from the network. When a truncated reply is processed, this incorrect boundary allows the decoder to read beyond the valid data and into stale memory contents from previous network operations.
This improper boundary handling directly violates fundamental security principles for network protocol parsing and creates an environment where malicious actors could potentially exploit the uninitialized memory read to extract sensitive information from the buffer. The vulnerability operates by allowing the ceph_decode_need() function to pass validation even with truncated responses, enabling the decoder to access second u64 values that originate from residual data left in the buffer by earlier messages rather than from the current network transmission.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially affect system stability and security posture. When the decode process reads from stale tail bytes, it may inadvertently expose kernel memory contents including cryptographic keys, session tokens, or other sensitive data that should remain confidential. This issue particularly affects systems running Ceph storage clusters where libceph clients communicate with monitor services, creating a potential attack surface for adversaries seeking to gather intelligence about the storage infrastructure.
The fix implemented addresses this vulnerability by changing the decode boundary from msg->front_alloc_len to msg->front.iov_len which represents the actual bytes that were read from the network connection. This change aligns the libceph implementation with other reply handlers within the same library and ensures that decoding operations are strictly limited to the data that was actually received rather than potentially uninitialized buffer space. This correction follows established security practices for protocol parsing and memory safety, reducing the risk of information leakage while maintaining proper operational functionality.
This vulnerability classifies under CWE-125 as "Uninitialized Memory Read" and demonstrates characteristics consistent with ATT&CK technique T1005 for data hijacking through memory access violations. The fix exemplifies defensive programming practices recommended in secure coding standards, particularly regarding buffer boundary validation and proper input sanitization during network protocol handling operations.