CVE-2026-89653
Description
A flaw was found in the Linux kernel's Ceph file system client. When decoding metadata server maps (MDSMap), the client fails to properly validate rank identifiers within export targets against protocol limits. A malicious or compromised Ceph storage monitor can send a crafted map that triggers an out-of-bounds write to a stack buffer. This flaw can lead to kernel memory corruption or a system crash, resulting in a Denial of Service (DoS).
Statement
This vulnerability is rated as Important because a rogue or compromised Ceph monitor can trigger stack-based memory corruption in the client kernel, potentially leading to a denial of service or arbitrary code execution. Exposure is limited to systems that actively mount Ceph filesystem shares using the in-kernel driver and communicate with untrusted or compromised storage cluster monitors. Typical Red Hat Enterprise Linux and OpenShift deployments that do not use the in-kernel CephFS client are not affected.
Mitigation
To mitigate this issue on systems where the kernel Ceph filesystem is not required, prevent the `ceph` module from being loaded:
1. Create a configuration file to disable autoloading of the module:
echo "install ceph /bin/true" > /etc/modprobe.d/disable-ceph.conf
2. If the module is currently loaded, unload it:
modprobe -r ceph
Warning: If the module is actively in use by mounted filesystems, unloading will fail and a system reboot is required to ensure the configuration takes effect.
Caveats: This workaround completely disables the in-kernel CephFS driver, preventing the host from mounting Ceph file storage. Userspace clients such as `ceph-fuse` are unaffected.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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