{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64541", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T15:36:31.795Z", "datePublished": "2026-07-27T20:10:34.439Z", "dateUpdated": "2026-08-17T04:57:17.774Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:57:17.774Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket\n\nsmc_cdc_rx_handler() looks up the connection by token under the link\ngroup's conns_lock, drops the lock, and then dereferences conn and the\nsmc_sock derived from it, ending in sock_hold(&smc->sk) inside\nsmc_cdc_msg_recv(). No reference is held across the lock release.\n\nThe only reference pinning the socket while the connection is\ndiscoverable in the link group is taken in smc_lgr_register_conn()\n(sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both\nunder conns_lock. Once the handler drops conns_lock, a concurrent\nclose() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn()\ncan drop that reference and free the smc_sock, so the handler's later\nsock_hold() runs on freed memory:\n\n WARNING: lib/refcount.c:25 at refcount_warn_saturate\n Workqueue: rxe_wq do_work\n refcount_warn_saturate (lib/refcount.c:25)\n smc_cdc_msg_recv (net/smc/smc_cdc.c:430)\n smc_cdc_rx_handler (net/smc/smc_cdc.c:502)\n smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445)\n tasklet_action_common (kernel/softirq.c:938)\n handle_softirqs (kernel/softirq.c:622)\n Kernel panic - not syncing: panic_on_warn set\n\nOnly SMC-R is affected. The SMC-D receive tasklet is stopped by\ntasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection\nis unregistered, so it cannot run concurrently with the free.\n\nTake the socket reference while still holding conns_lock, so the\nregistration reference can no longer be the last one, and drop it once\nthe handler is done." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable handler is driven entirely by a CDC control message sent by the remote SMC-R peer over the RDMA link, with an attacker-chosen `token` field and no local syscall involvement. SMC-R runs over RoCEv2 (IP/UDP-routable, port 4791) with the CLC handshake over plain TCP, and SMC-Rv2 explicitly supports non-local/routed peers, so the attacker need not share an L2 segment.\nAC:L - The attacker controls both sides of the race: it chooses when to emit CDC messages and which connection to target (the alert token is disclosed to it in the CLC accept/confirm), and it can drive the teardown side itself via CDC close/abort flags into `smc_close_passive_work()` or a stale seqno with `failover_validation` into `abort_work` -> `smc_conn_kill()`. The race can be retried indefinitely across many connections in the same link group, and was reproduced in practice with soft-RoCE.\nPR:N - Establishing an SMC-R connection to a listening SMC socket requires no credentials — SMC has no authentication layer of its own, exactly like plain TCP. Everything after connection establishment (sending CDC messages with a chosen token, signalling close/abort) is available to an unauthenticated peer.\nUI:N - The CDC message is processed in a softirq tasklet from the RDMA completion queue with no involvement from any local user or application action. No victim interaction of any kind is needed.\nS:U - The corruption is confined to kernel memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed. This is a standard in-kernel use-after-free.\nC:H - The freed `smc_sock` is reused type-safely as another live socket, so attacker-supplied cursors applied by `smc_cdc_msg_recv_action()` break the `0 <= bytes_to_rcv <= rmb_desc->len` invariant and make `smc_rx_recvmsg()` hand stale RMB contents to userspace, while the urgent-data path reads `*(base + conn->urg_curs.count - 1)` at an attacker-chosen offset. Once the slab page is reclaimed after the RCU grace period, reuse is unconstrained, giving a general kernel-memory read primitive.\nI:H - `sock_hold()` on an already-zero refcount followed by `sock_put()` re-enters `sk_free()`, yielding a double free, and the handler additionally writes `sk_err`/`sk_shutdown`, makes indirect calls through `sk_data_ready()`/`sk_write_space()`, and `queue_work()`s a freed `work_struct`. These are classic heap-spray and control-flow-hijack primitives leading to arbitrary kernel write.\nA:H - The reported symptom is `refcount_warn_saturate` from `smc_cdc_msg_recv()`, which is an immediate kernel panic on `panic_on_warn` systems, and dereferencing freed memory in softirq context otherwise oopses. The attacker can trigger it repeatedly without authentication." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/smc/smc_cdc.c" ], "versions": [ { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "8de4f665d0febfb92803dece377791a563fc7041", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "8145b432136285e01091815b48ceb2dae261f262", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "1951bffbc6493ec34cff3956b29d4bc6606904a6", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "647b19e5cc145a2f1f685ae8ff3805a17356888c", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "472e9d7c0d5b03be3ff91ff941f57da822b031bc", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "ce5aa8084329351086894aa34d77e40301d5bd3d", "status": "affected", "versionType": "git" }, { "version": "d7b0e37c1ac152905b18a5b9506179091a35b0b6", "lessThan": "9d160b35cc34a2ba8229d07651468a7848325135", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/smc/smc_cdc.c" ], "versions": [ { "version": "4.18", "status": "affected" }, { "version": "0", "lessThan": "4.18", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/8de4f665d0febfb92803dece377791a563fc7041" }, { "url": "https://git.kernel.org/stable/c/8145b432136285e01091815b48ceb2dae261f262" }, { "url": "https://git.kernel.org/stable/c/1951bffbc6493ec34cff3956b29d4bc6606904a6" }, { "url": "https://git.kernel.org/stable/c/647b19e5cc145a2f1f685ae8ff3805a17356888c" }, { "url": "https://git.kernel.org/stable/c/472e9d7c0d5b03be3ff91ff941f57da822b031bc" }, { "url": "https://git.kernel.org/stable/c/3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb" }, { "url": "https://git.kernel.org/stable/c/ce5aa8084329351086894aa34d77e40301d5bd3d" }, { "url": "https://git.kernel.org/stable/c/9d160b35cc34a2ba8229d07651468a7848325135" } ], "title": "net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket", "x_generator": { "engine": "bippy-1.2.0" } } } }