CVE-2026-89699

A flaw was found in the Linux kernel's Network File System Daemon (nfsd) when handling NFSv4 CREATE operations. A remote attacker can exploit this by sending a crafted request with an oversized symbolic link (symlink) target length. This unbounded length can force the kernel to allocate a large amount of memory, leading to a denial of service (DoS) condition on the system.

A flaw of MODERATE impact was found in the Linux kernel's Network File System daemon (nfsd) as shipped in Red Hat Enterprise Linux and in the Red Hat Enterprise Linux CoreOS (RHCOS) kernels used by OpenShift Container Platform. When handling NFSv4 CREATE operations, the nfsd4_decode_create() function accepts an unbounded symlink target length (cr_datalen) from the wire for NF4LNK objects. A remote attacker can send a crafted request with an oversized symlink target, forcing the kernel to allocate up to the maximum RPC payload size (several MiB) per COMPOUND operation, an allocation that persists until compound teardown. Although the VFS rejects oversized targets with ENAMETOOLONG, the memory has already been allocated by that point, so repeated crafted requests can be used to consume kernel memory and cause a denial of service. The impact is limited to availability; there is no effect on confidentiality or integrity. The upstream CVE record assigns this issue a severity of Important (CVSS 7.5, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), while Red Hat rates it Moderate (CVSS 5.5) based on its assessment of the prerequisites for exploitation and the availability-only impact. Fixes for the affected Red Hat Enterprise Linux and OpenShift Container Platform streams are currently deferred because this is a Moderate severity flaw with a CVSS score below 7.0, for which trackers are not filed absent a higher CVSS score; the residual risk is a denial of service of the nfsd server by clients able to submit crafted NFSv4 CREATE requests. The Red Hat Enterprise Linux 6 stream is out of support scope.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.