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
A Linux Ceph storage client can become stuck after a connection failure interrupts a sparse read. Retried reads may be mistaken for continuations of the failed reply, causing recurring errors and loss of storage availability. The supplied CVSS score is 7.5, reflecting high availability impact without identified confidentiality or integrity impact.
Executive priority
Treat as high priority for production systems whose services depend on Linux Ceph client availability. Expedite verification and patching where a storage-client failure could interrupt critical workloads. Lower the priority for systems that do not use libceph or where the applicable stable fix is already confirmed.
Technical view
libceph maintains sparse-read progress separately from messenger connection state. Before the fix, osd_fault() did not reset that progress after connection loss or sparse-read errors. A retried operation could therefore parse a new reply using stale state, enter a persistent failure condition, and repeatedly encounter length mismatches and socket read errors. The fix resets sparse-read state before retrying.
Likely exposure
Exposure is most relevant to systems using the Linux libceph OSD client for Ceph sparse-read operations on affected kernels. A connection fault during reply processing is required for the described failure. The supplied version data is ambiguous, so kernel build and patch status should be verified directly rather than inferred solely from version numbers.
Exploitation context
The supplied CVSS vector describes network reachability, low complexity, no privileges, no user interaction, and availability-only impact. However, the sources do not establish active exploitation, public exploit availability, or inclusion in CISA KEV. They also do not demonstrate that arbitrary internet clients can trigger the condition.
Researcher notes
The failure is a retry-state synchronization defect, not evidence of data disclosure or modification. Useful investigation should focus on branch-specific fix ancestry, sparse-read usage, connection-fault timing, and whether clients recover after faults. The provided affected-version list contains unclear entries and should not be treated as a complete distribution-level applicability statement.
Mitigation direction
Apply the applicable Linux stable fix referenced for the deployed kernel branch.
Obtain distribution-specific kernel guidance when commit inclusion cannot be confirmed.
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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