{"id":"CVE-2026-89546","title":"SUNRPC: close backchannel before destroying callback service","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: close backchannel before destroying callback service\n\nA backchannel receive can complete a request while the NFS callback\nservice is being torn down.  xprt_comp…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-911"],"vendor":"Linux","product":"Linux","affected":["Linux >= 441244d4273a8037b265fd254dfdaca5fa736ee2 < 6debde9e3e6ae21dcca75837b4247b13ca4ea2b8","Linux >= 441244d4273a8037b265fd254dfdaca5fa736ee2 < 3674f780f47d2906b5a0f7199b66973067bdfeca","Linux 6.19"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:48:37.920Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89546","references":[{"url":"https://git.kernel.org/stable/c/6debde9e3e6ae21dcca75837b4247b13ca4ea2b8"},{"url":"https://git.kernel.org/stable/c/3674f780f47d2906b5a0f7199b66973067bdfeca"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89546.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89546"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532175"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89546"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89546"}],"tags":["cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.00553,"epssPercentile":0.46015,"scores":{"cna":9.8,"vendor":5.3},"ingestedAt":"2026-09-14T15:23:07.474Z","slug":"CVE-2026-89546","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: close backchannel before destroying callback service\n\nA backchannel receive can complete a request while the NFS callback\nservice is being torn down.  xprt_complete_bc_request() removes the\nrequest from bc_pa_list, drops bc_alloc_count, marks the request in use,\nand then asks xprt_enqueue_bc_request() to hand it to the callback\nservice.\n\nIf teardown has already cleared xprt->bc_serv, xprt_enqueue_bc_request()\ncurrently returns without enqueueing or freeing the committed request.\nThe xprt_get() taken on entry is leaked as well.  If the producer wins\nthe race before bc_serv is cleared, it can also enqueue onto sv_cb_list\nafter nfs_callback_down() has stopped the callback threads, leaving the\nrequest linked to a svc_serv that is about to be freed.\n\nClose the producer side before callback threads are stopped.  Add\nxprt_svc_shutdown_bc() to clear xprt->bc_serv under bc_pa_lock, and call\nit on callback shutdown and callback-start failure before stopping the\nservice threads.  Requests that lose the NULL transition in\nxprt_enqueue_bc_request() are released through the normal backchannel\nfree path after balancing bc_slot_count.  Finally, drain any remaining\nsv_cb_list requests after the callback threads have stopped and before\nsvc_destroy() frees the service.\n\n## Affected\n\n- `Linux >= 441244d4273a8037b265fd254dfdaca5fa736ee2 < 6debde9e3e6ae21dcca75837b4247b13ca4ea2b8`\n- `Linux >= 441244d4273a8037b265fd254dfdaca5fa736ee2 < 3674f780f47d2906b5a0f7199b66973067bdfeca`\n- `Linux 6.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat OpenShift Container Platform 4 · updated 2026-09-13 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89546.json)","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":224713,"id":"CVE-2026-89546","ts":1792401490811,"field":"cvss","old":"5.3","new":"9.8"},{"seq":224712,"id":"CVE-2026-89546","ts":1792401490811,"field":"severity","old":"medium","new":"critical"},{"seq":202885,"id":"CVE-2026-89546","ts":1789403732806,"field":"cvss","old":"9.8","new":"5.3"},{"seq":202884,"id":"CVE-2026-89546","ts":1789403732806,"field":"severity","old":"critical","new":"medium"},{"seq":197951,"id":"CVE-2026-89546","ts":1789384321110,"field":"cvss","old":"5.3","new":"9.8"},{"seq":197950,"id":"CVE-2026-89546","ts":1789384321110,"field":"severity","old":"medium","new":"critical"},{"seq":183490,"id":"CVE-2026-89546","ts":1789356675584,"field":"cvss","old":"9.8","new":"5.3"},{"seq":183489,"id":"CVE-2026-89546","ts":1789356675584,"field":"severity","old":"critical","new":"medium"},{"seq":153348,"id":"CVE-2026-89546","ts":1789285350145,"field":"cvss","old":null,"new":"9.8"},{"seq":153347,"id":"CVE-2026-89546","ts":1789285350145,"field":"severity","old":"none","new":"critical"},{"seq":147650,"id":"CVE-2026-89546","ts":1789270211740,"field":"cvss","old":null,"new":"5.3"},{"seq":147649,"id":"CVE-2026-89546","ts":1789270211740,"field":"severity","old":"none","new":"medium"},{"seq":109404,"id":"CVE-2026-89546","ts":1789183731783,"field":"cvss","old":null,"new":"5.3"},{"seq":109403,"id":"CVE-2026-89546","ts":1789183731783,"field":"severity","old":"none","new":"medium"}]}