{"id":"CVE-2026-72464","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-72464","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.","published":"2026-08-15T05:57:08.080Z","modified":"2026-08-16T03:48:48.371424478Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.1.178"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/007b4da2f38dcc16a13265416f4ca9f179bab610"},{"type":"WEB","url":"https://git.kernel.org/stable/c/19fae02b272ee4bcdfb5db57f402d28f1697167a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4322fd9645ee769ad29ce5caea74a1cd9b17269d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/abc011ddaf1617e3e82d8a1e87daa7ddbfb9bac5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d7c531ab477ae94fd03771d707fd29c787408039"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ef6fb8a5c521f1a07f85202d13e8f2898f247362"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72464.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72464"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-16T03:48:48.371424478Z"}}