{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40139","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.171Z","datePublished":"2025-11-12T10:23:24.216Z","dateUpdated":"2026-08-05T12:08:01.554Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:08:01.554Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().\n\nsmc_clc_prfx_set() is called during connect() and not under RCU\nnor RTNL.\n\nUsing sk_dst_get(sk)->dev could trigger UAF.\n\nLet's use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock()\nafter kernel_getsockname().\n\nNote that the returned value of smc_clc_prfx_set() is not used\nin the caller.\n\nWhile at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu()\nnot to touch dst there."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - `smc_clc_prfx_set()` is only reached from the client side of the CLC handshake, via `connect()` on a locally created AF_SMC socket (`smc_connect` → `__smc_connect` → `smc_clc_send_proposal`). The attacker must have local code execution to initiate the connection, so the vector is Local even though the leaked bytes are subsequently sent to a remote peer.\nAC:L - The attacker drives both sides of the race — one thread loops `connect()` on AF_SMC sockets (the stale `dst->dev` dereference), while another repeatedly creates and deletes net_devices to force `dst_dev_put()`/`free_netdev()`, which unprivileged users can do freely inside a user namespace with CAP_NET_ADMIN. No condition depends on state outside the attacker's influence, and the window is widened at will by using non-blocking connect so the work runs in `smc_connect_work`.\nPR:L - `smc_create()` performs no capability check and `MODULE_ALIAS_NETPROTO(PF_SMC)` lets any unprivileged user autoload the module; the netdev teardown side needs CAP_NET_ADMIN, which is obtainable by an ordinary user via `unshare -Urn` and therefore counts as Low, not High.\nUI:N - The attacker's own process performs every step — creating the SMC socket, connecting to a listener it controls, and tearing down the device — with no action required from any other user or administrator.\nS:U - The use-after-free touches the freed `net_device` slab and the `in_device`/`inet6_dev` structures it points to, all within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed `net_device` is dereferenced and its `ifa_list`/`addr_list` walked, and a reclaimed slab can be groomed with attacker-controlled data, yielding an arbitrary kernel-memory read; worse, `smc_clc_prfx_set6_rcu()` copies up to 8 prefixes out of that freed memory into the CLC Proposal that `smc_clc_send_proposal()` transmits, exfiltrating freed kernel bytes onto the wire.\nI:H - A use-after-free on a `net_device` is a heap-corruption primitive — the reclaimed object's contents are attacker-influenceable through heap spraying and the code follows pointers out of it (`dev->ip_ptr`, `dev->ip6_ptr`, list heads), which can be groomed into an arbitrary write and control-flow hijack.\nA:H - Dereferencing the freed device and walking a bogus `in_dev`/`inet6_dev` address list reliably produces a kernel oops or panic, or an unbounded list walk that hangs the CPU, and the attacker can repeat the attempt indefinitely."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_clc.c"],"versions":[{"version":"a046d57da19f812216f393e7c535f5858f793ac3","lessThan":"0736993bfe5c7a9c744ae3fac62d769dfdae54e1","status":"affected","versionType":"git"},{"version":"a046d57da19f812216f393e7c535f5858f793ac3","lessThan":"935d783e5de9b64587f3adb25641dd8385e64ddb","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_clc.c"],"versions":[{"version":"4.11","status":"affected"},{"version":"0","lessThan":"4.11","status":"unaffected","versionType":"semver"},{"version":"6.17.3","lessThanOrEqual":"6.17.*","status":"unaffected","versionType":"semver"},{"version":"6.18","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":"4.11","versionEndExcluding":"6.17.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"6.18"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/0736993bfe5c7a9c744ae3fac62d769dfdae54e1"},{"url":"https://git.kernel.org/stable/c/935d783e5de9b64587f3adb25641dd8385e64ddb"}],"title":"smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().","x_generator":{"engine":"bippy-1.2.0"}}}}