{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-72464", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-72464" ], "published": "2026-08-15T06:04:33Z", "summary": "xprtrdma: Repost Receive buffers for malformed replies", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nxprtrdma: Repost Receive buffers for malformed replies\n\nrpcrdma_wc_receive() decrements the transport's Receive count for\nevery completion before it dispatches a successful Receive to\nrpcrdma_reply_handler(). The handler must post a replacement\nReceive WR before returning unless ownership of the rep has moved\nelsewhere, as on the backchannel path.\n\nCommit 2ae50ad68cd7 (\"xprtrdma: Close window between waking RPC\nsenders and posting Receives\") moved the Receive refill out of\nrpcrdma_wc_receive(), where it had run ahead of every reply, into\nrpcrdma_reply_handler() so that the responder's credit grant could\nbe parsed before reposting. The bad-version and short-reply exits\nnever reach that refill: they recycle the rep and return without\ncalling rpcrdma_post_recvs().\n\nA remote peer can therefore drain the client's posted Receive\nqueue by sending a sustained stream of replies that are shorter\nthan the fixed transport header or that carry an unrecognized\nRPC/RDMA version. Each such reply consumes one posted Receive\nwithout replacing it. Once the queue empties, the peer's next\nSend finds no posted Receive and the transport stalls until\nreconnect.\n\nRoute both malformed-reply exits through the shared repost tail\nafter recycling the rep, refilling against buf->rb_credits, the\nmost recent accepted credit grant. Neither exit updates the\ncongestion window, so RPCs admitted under the previous grant\nremain in flight awaiting replies. A smaller refill target would\nlet a stream of malformed replies ratchet the posted Receive count\ndown to the batch floor while the congestion window still admits\nrb_credits RPCs; a burst of valid replies to those RPCs could then\noverrun the posted Receives, and because the client connects with\nrnr_retry_count of zero, a single RNR NAK terminates the\nconnection. Refilling against rb_credits also restores the target\nthat applied to malformed replies before commit 2ae50ad68cd7\n(\"xprtrdma: Close window between waking RPC senders and posting\nReceives\") when rpcrdma_post_recvs() computed it from rb_credits\ninternally. rb_credits is at least one from connection\nestablishment onward, so the repost path always keeps Receives\nposted.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.178", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-72464" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ef6fb8a5c521f1a07f85202d13e8f2898f247362" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4322fd9645ee769ad29ce5caea74a1cd9b17269d" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/19fae02b272ee4bcdfb5db57f402d28f1697167a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/007b4da2f38dcc16a13265416f4ca9f179bab610" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d7c531ab477ae94fd03771d707fd29c787408039" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/abc011ddaf1617e3e82d8a1e87daa7ddbfb9bac5" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-17T05:50:24Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.5, "cvss_v3_severity": "High", "scenario": "AV:N - Malicious or compromised NFS/RDMA server sends malformed RPC reply messages over an established RDMA connection; the kernel client processes them in rpcrdma_wc_receive()/rpcrdma_reply_handler() without any local access.\nAC:L - Remote server reliably triggers the bug by streaming replies shorter than the fixed RPC/RDMA header or carrying an unrecognized version; each consumes a posted Receive without reposting a replacement.\nPR:N - Attacker needs no credentials on the victim host, only the ability to act as the connected RDMA peer (e.g., a malicious or compromised NFS server the client has mounted).\nUI:N - Exploitation requires only an active NFS-over-RDMA client session; no additional victim action is needed beyond an existing mount/connection used for normal I/O.\nS:U - Impact is confined to SunRPC/RDMA transport availability on the NFS client; it does not cross VM, container, or kernel/user security boundaries.\nC:N - No memory corruption or out-of-bounds access occurs; short or bad-version replies are detected during header decode and the buffer is recycled without disclosing kernel data.\nI:N - The flaw only fails to repost Receive buffers after malformed replies; it does not corrupt memory, alter RPC payloads, or enable arbitrary kernel writes.\nA:H - Sustained malformed replies drain all posted Receives, stalling the transport until reconnect; a burst of valid replies can trigger RNR NAK and disconnect (rnr_retry_count=0), denying NFS/RDMA service." } } }