CVE-2026-89530
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
A vulnerability exists in the Linux kernel's svcrdma module (RPC-over-RDMA). A client can request a reply without providing a Write list or Reply chunk, causing the linearization function to copy past the end of the sc_xprt_buf buffer and corrupt adjacent slab memory. The oversized length is then stored in sc_sges[0].length and posted, causing the device to read beyond the mapped region.
Risk Assessment
The vulnerability can lead to kernel memory corruption and potential code execution or denial of service (kernel panic) on systems acting as NFS/RDMA servers. It requires a remote, unauthenticated RPC-over-RDMA client, increasing the exploitation risk.
Recommendation
Update the Linux kernel to a version containing the fix that rejects oversized pull-up replies with -E2BIG and fails the request with ERR_CHUNK. If updating is not possible, consider restricting access to RPC-over-RDMA services to trusted clients.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: svcrdma: Reject inline replies that overflow the pull-up buffer An RPC-over-RDMA client can request a reply, such as an NFS READ payload, without providing a Write list or a Reply chunk to carry it. When such a reply needs more scatter/gather entries than the device's Send Queue supports, svc_rdma_pull_up_needed() selects pull-up and svc_rdma_pull_up_reply_msg() linearizes the whole reply into sctxt->sc_xprt_buf. That buffer is only sc_max_req_size bytes, while the reply on this path is bounded only by the client's request, so svc_rdma_xb_linearize() copies past the end of the buffer and corrupts adjacent slab memory. The oversized length is then stored in sc_sges[0].length and posted, so the device also reads beyond the mapped region. The SGE-exhaustion branch is the only pull-up path that can exceed the buffer: the threshold branch pulls up only replies smaller than RPCRDMA_PULLUP_THRESH, and replies that fit the device's SGE budget are sent directly without linearization. Make svc_rdma_pull_up_needed() report -E2BIG when the reply it would pull up cannot fit sc_max_req_size, and fail the request with ERR_CHUNK as RFC 8166 Section 4.5.3 directs rather than dropping the connection. The helper no longer answers a simple yes/no question: it now reports pull-up, no pull-up, or -E2BIG for a reply too large to linearize. Rename svc_rdma_pull_up_needed() to svc_rdma_check_pull_up() so its name no longer implies a boolean predicate.