Horizon Alert
Summary of the vulnerability and why it matters
This advisory addresses a vulnerability in the Linux kernel's CephFS implementation that could be triggered when CephFS is re-exported over NFS. An attacker could potentially exploit this by sending malformed data, leading to a buffer overflow and a system crash or unpredictable behavior. The main concern is confirming relevance and exposure given the specific conditions required for exploitation.
- Overflows in file name handling in CephFS.
- Critical flaw impacting system stability if exploited.
- Confirm if your NFS re-exports of CephFS are affected.
Attack Path
How an attacker could exploit the issue
An attacker could exploit this by manipulating a Ceph Metadata Server (MDS) to send an excessively long file name during a lookup. This crafted name would overflow a buffer in the client's NFS export handling, leading to a crash.
- Entry condition: A CephFS mount re-exported over NFS.
- Trigger point: A malicious MDS providing a long name.
- Resulting risk: Out-of-bounds write, potential system crash.
Live Threat
Current exploitation, exposure, and threat context
When a CephFS mount is re-exported over NFS, a malicious or compromised Ceph MDS could overflow a buffer on the NFS client. This could lead to an out-of-bounds write in the kernel when copying a file name, potentially impacting system stability.
- Kernel memory corruption.
- Malicious MDS supplies oversized name.
- System instability or crash.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability impacts systems where CephFS is re-exported over NFS, pointing to potential ownership by infrastructure, platform, or storage teams responsible for managing Ceph and NFS services. The immediate priority is to identify all instances of this specific configuration, confirm business criticality and external reachability, and assign an accountable owner before planning remediation.
- Infrastructure and platform teams own the issue.
- Verify CephFS NFS re-export configurations.
- Plan remediation based on exposure and criticality.
