CVE-2026-23136: libceph: reset sparse-read state in osd_fault()
In the Linux kernel, the following vulnerability has been resolved:
libceph: reset sparse-read state in osd_fault()
When a fault occurs, the connection is abandoned, reestablished, and any
pending operations are retried. The OSD client tracks the progress of a
sparse-read reply using a separate state machine, largely independent of
the messenger's state.
If a connection is lost mid-payload or the sparse-read state machine
returns an error, the sparse-read state is not reset. The OSD client
will then interpret the beginning of a new reply as the continuation of
the old one. If this makes the sparse-read machinery enter a failure
state, it may never recover, producing loops like:
libceph: [0] got 0 extents
libceph: data len 142248331 != extent len 0
libceph: osd0 (1)...:6801 socket error on read
libceph: data len 142248331 != extent len 0
libceph: osd0 (1)...:6801 socket error on read
Therefore, reset the sparse-read state in osd_fault(), ensuring retries
start from a clean state.
Security readout for executives and security teams
Plain-English summary
This Linux kernel issue can cause systems using the kernel Ceph client to get stuck retrying reads after a connection fault. The disclosed impact is availability only: affected systems may loop on failed reads rather than recovering cleanly. No source in the bundle supports active exploitation.
Executive priority
Treat this as high priority for Ceph-dependent production workloads because storage availability can be affected. It is not described as data theft or privilege escalation, and exploitation evidence is absent in the provided sources.
Technical view
libceph’s OSD client did not reset sparse-read state in osd_fault(). After a mid-payload connection loss or sparse-read error, retried operations could parse a new reply as continuation data, driving persistent sparse-read failure and socket read loops. The kernel fix resets sparse-read state before retry.
Likely exposure
Exposure is most likely on Linux hosts using the in-kernel Ceph client path against OSDs, such as Ceph-backed storage consumers. The source bundle lists Linux kernel versions as affected but does not provide distribution-specific package status.
Exploitation context
The CVSS vector is network-adjacent in practical storage terms but recorded as AV:N, low complexity, no privileges, and no user interaction. The bundle does not identify public exploitation, KEV listing, or a weaponized technique.
Researcher notes
The key failure mode is stale sparse-read state across osd_fault() reconnection and retry. Validate remediation by mapping downstream kernel builds to the upstream stable commits; the bundle does not include distro backport metadata or proof-of-concept details.
Mitigation direction
Apply vendor kernel updates that include the referenced stable fixes.
Prioritize systems using kernel Ceph clients for production storage.
Check distribution advisories for package names and fixed build numbers.
Consider reducing exposure of Ceph storage networks where operationally feasible.
Validation and detection
Inventory Linux kernel versions on Ceph client systems.
Identify hosts using in-kernel Ceph, CephFS, or RBD client paths.
Review logs for repeated libceph sparse-read or socket read errors.
Confirm installed kernels include one of the referenced stable commits.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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CVSS vector scores
1 official score
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