CVE-2026-89657 Linux CVE debrief

Who should care

Linux kernel administrators and Ceph users should assess their exposure and prioritize patching vulnerable versions to prevent potential crashes. Defenders should prioritize patching vulnerable Linux kernel versions to prevent potential crashes caused by malformed Ceph OSD replies. The vulnerability can be exploited by a malicious or compromised authenticated Ceph OSD peer to crash a kernel Ceph client via a malformed sparse-read reply.

Why it matters

A vulnerability in the Linux kernel's libceph component can be exploited to crash kernel Ceph clients. Defenders should prioritize patching vulnerable versions and verify Ceph client configurations to prevent potential crashes.

• Potential crashes of kernel Ceph clients
• Increased risk of denial-of-service attacks
• Need for verification of Ceph client configurations
• Priority for patching vulnerable Linux kernel versions

Technical summary

The vulnerability exists in the libceph component of the Linux kernel, where the OSD extent maps are not properly validated before advancing the cursor. This can lead to a crash of the kernel Ceph client when a malformed authenticated OSD reply is received. The vulnerability has a high CVSS score of 7.5 and is considered a high-severity issue. The vulnerability can be exploited by a malicious or compromised authenticated Ceph OSD peer to crash a kernel Ceph client via a malformed sparse-read reply. Defenders should prioritize patching vulnerable Linux kernel versions to prevent potential crashes caused by malformed Ceph OSD replies.

Defensive priority

Defenders should prioritize patching vulnerable Linux kernel versions to prevent potential crashes caused by malformed Ceph OSD replies.

Recommended defensive actions

• Patch vulnerable Linux kernel versions
• Verify Ceph client configurations
• Monitor for suspicious Ceph OSD activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability, including its impact and affected versions. The Linux kernel's libceph component is vulnerable to a crash caused by a malformed authenticated OSD reply. The vulnerability is caused by the lack of proper validation of OSD extent maps before advancing the cursor. The CVE record was published on 2026-09-11T19:45:46.118Z and has not been modified since then. The source item provides additional details on the vulnerability, including its description and summary.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.