{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63978", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.025Z", "datePublished": "2026-07-19T14:56:02.484Z", "dateUpdated": "2026-08-09T18:34:55.102Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-09T18:34:55.102Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/handshake: Drain pending requests at net namespace exit\n\nThe arguments to list_splice_init() in handshake_net_exit() are\nreversed. The call moves the local empty \"requests\" list onto\nhn->hn_requests, leaving the local list empty, so the subsequent\ndrain loop runs zero iterations. Pending handshake requests that\nhad not yet been accepted are not torn down when the net namespace\nis destroyed; each one keeps a reference on a socket file and on\nthe handshake_req allocation.\n\nPass the source and destination in the documented order\n(list_splice_init(list, head) moves list onto head) so the pending\nlist is transferred to the local scratch list and drained through\nhandshake_complete().\n\nFixing the splice direction exposes a list-corruption race. After\nthe splice each req->hr_list still has non-empty link pointers,\nthreading the stack-local scratch list rather than hn_requests.\nA concurrent handshake_req_cancel() -- for example, from sunrpc's\nTLS timeout on a kernel socket whose netns reference was not\ntaken -- finds the request through the rhashtable, calls\nremove_pending(), and sees !list_empty(&req->hr_list).\n__remove_pending_locked() then list_del_init()s an entry off the\nscratch list while the drain iterates, corrupting it. The same\ncall arriving after the drain loop has run list_del() on an\nentry hits LIST_POISON instead.\n\nHave remove_pending() check HANDSHAKE_F_NET_DRAINING under\nhn_lock and report not-found when drain is in progress. The\ndrain has already taken ownership; handshake_complete()'s existing\ntest_and_set on HANDSHAKE_F_REQ_COMPLETED still arbitrates\nbetween drain and cancel for who calls the consumer's hp_done. Use\nlist_del_init() rather than list_del() in the drain so req->hr_list\ndoes not carry LIST_POISON after drain releases the entry.\n\nThe DRAINING guard in remove_pending() makes cancel return false,\nbut cancel still falls through to test_and_set_bit on\nHANDSHAKE_F_REQ_COMPLETED and drops the request's hr_file reference.\nWithout another pin, if that is the last reference, sk_destruct frees\nthe request while it is still linked on the drain loop's local list.\nPin each request's hr_file under hn_lock before releasing the list,\nand drop that drain pin after the loop finishes with the request." } ], "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 - Pending handshake requests are created by network-facing kernel TLS consumers (nfsd via `tls_server_hello_x509()` in sunrpc, nvmet-tcp via `tls_server_hello_psk()`), reachable from unauthenticated remote TCP connections before credentials are verified; the bug fires when that namespace is torn down while those requests remain pending.\nAC:L - An attacker can reliably orchestrate the failure by opening TLS connections to leave handshakes pending, then destroying the namespace (user/net namespace or container teardown) and waiting for the predictable sunrpc/NVMe TLS timeout to invoke `handshake_req_cancel()` against freed per-net state.\nPR:N - No server-side privileges are required to reach the vulnerable path—remote peers can initiate the pre-authentication TLS handshake that queues pending requests; namespace teardown is also achievable without init-namespace root via user namespaces granting CAP_SYS_ADMIN.\nUI:N - Exploitation requires no victim interaction beyond the attacker (or orchestrator) initiating connections and namespace lifecycle events; no end-user actions such as mounting filesystems or opening files are needed.\nS:U - Impact is confined to kernel memory corruption and host availability within the same kernel security domain; it does not cross a VM, container sandbox, or IOMMU boundary to affect a separate security authority.\nC:H - Undrained requests leave `handshake_req` objects and freed `handshake_net` state reachable through the global rhashtable; concurrent `handshake_req_cancel()` dereferences freed `hn_lock`/`hn_requests` and can hit LIST_POISON, constituting use-after-free with arbitrary-read potential.\nI:H - The reversed `list_splice_init()` and ensuing drain/cancel races corrupt kernel linked lists and free in-use `handshake_req` structures while still linked, enabling memory corruption exploitable for control-flow hijacking.\nA:H - List corruption and use-after-free on namespace exit or concurrent cancel reliably cause kernel oops/panic or deadlock-class failures, and repeated namespace churn with pending handshakes enables sustained denial of service on the host." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/handshake/netlink.c", "net/handshake/request.c" ], "versions": [ { "version": "3b3009ea8abb713b022d94fba95ec270cf6e7eae", "lessThan": "9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd", "status": "affected", "versionType": "git" }, { "version": "3b3009ea8abb713b022d94fba95ec270cf6e7eae", "lessThan": "2bf24a7e190aae0ea47c78099938ae056c622e44", "status": "affected", "versionType": "git" }, { "version": "3b3009ea8abb713b022d94fba95ec270cf6e7eae", "lessThan": "8c35539db0ab0bfa1ea44efab00b053261a69469", "status": "affected", "versionType": "git" }, { "version": "3b3009ea8abb713b022d94fba95ec270cf6e7eae", "lessThan": "ea5fe6a73ca57e5150b8a38b341aef2636eb72f0", "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/handshake/netlink.c", "net/handshake/request.c" ], "versions": [ { "version": "6.4", "status": "affected" }, { "version": "0", "lessThan": "6.4", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.44", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "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": "6.4", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4", "versionEndExcluding": "6.18.44" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/9ec20c9a5a04f2c3f1cf65d21f886d7aaa6189cd" }, { "url": "https://git.kernel.org/stable/c/2bf24a7e190aae0ea47c78099938ae056c622e44" }, { "url": "https://git.kernel.org/stable/c/8c35539db0ab0bfa1ea44efab00b053261a69469" }, { "url": "https://git.kernel.org/stable/c/ea5fe6a73ca57e5150b8a38b341aef2636eb72f0" } ], "title": "net/handshake: Drain pending requests at net namespace exit", "x_generator": { "engine": "bippy-1.2.0" } } } }