{"id":"CVE-2023-53585","state":"PUBLISHED","title":"bpf: reject unhashed sockets in bpf_sk_assign","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: reject unhashed sockets in bpf_sk_assign\n\nThe semantics for bpf_sk_assign are as follows:\n\n    sk = some_lookup_func()\n    bpf_sk_assign(skb, sk)\n    bpf_sk_release(sk)\n\nThat is, the sk is not consumed by bpf_sk_assign. The function\ntherefore needs to make sure that sk lives long enough to be\nconsumed from __inet_lookup_skb. The path through the stack for a\nTCPv4 packet is roughly:\n\n  netif_receive_skb_core: takes RCU read lock\n    __netif_receive_skb_core:\n      sch_handle_ingress:\n        tcf_classify:\n          bpf_sk_assign()\n      deliver_ptype_list_skb:\n        deliver_skb:\n          ip_packet_type->func == ip_rcv:\n            ip_rcv_core:\n            ip_rcv_finish_core:\n              dst_input:\n                ip_local_deliver:\n                  ip_local_deliver_finish:\n                    ip_protocol_deliver_rcu:\n                      tcp_v4_rcv:\n                        __inet_lookup_skb:\n                          skb_steal_sock\n\nThe existing helper takes advantage of the fact that everything\nhappens in the same RCU critical section: for sockets with\nSOCK_RCU_FREE set bpf_sk_assign never takes a reference.\nskb_steal_sock then checks SOCK_RCU_FREE again and does sock_put\nif necessary.\n\nThis approach assumes that SOCK_RCU_FREE is never set on a sk\nbetween bpf_sk_assign and skb_steal_sock, but this invariant is\nviolated by unhashed UDP sockets. A new UDP socket is created\nin TCP_CLOSE state but without SOCK_RCU_FREE set. That flag is only\nadded in udp_lib_get_port() which happens when a socket is bound.\n\nWhen bpf_sk_assign was added it wasn't possible to access unhashed\nUDP sockets from BPF, so this wasn't a problem. This changed\nin commit 0c48eefae712 (\"sock_map: Lift socket state restriction\nfor datagram sockets\"), but the helper wasn't adjusted accordingly.\nThe following sequence of events will therefore lead to a refcount\nleak:\n\n1. Add socket(AF_INET, SOCK_DGRAM) to a sockmap.\n2. Pull socket out of sockmap and bpf_sk_assign it. Since\n   SOCK_RCU_FREE is not set we increment the refcount.\n3. bind() or connect() the socket, setting SOCK_RCU_FREE.\n4. skb_steal_sock will now set refcounted = false due to\n   SOCK_RCU_FREE.\n5. tcp_v4_rcv() skips sock_put().\n\nFix the problem by rejecting unhashed sockets in bpf_sk_assign().\nThis matches the behaviour of __inet_lookup_skb which is ultimately\nthe goal of bpf_sk_assign().","publishedAt":"2025-10-04T15:44:01.022Z","updatedAt":"2026-05-11T19:47:54.787Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"791a12102e5191dcb6ce0b3a99d71b5a2802d12a","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"7dcbc0bb0e5cc1823923744befce59ac353135e6","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"c0ce0fb76610d5fad31f56f2ca8241a2a6717a1b","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"8aa43cfbb68b25119d2ced14ec717173e2901fa2","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"3d4522f59fb748a54446846522941a4f09da63e9","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"67312adc96b5a585970d03b62412847afe2c6b01","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"5.10.195","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.132","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.53","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.4.16","status":"unaffected","lessThanOrEqual":"6.4.*","versionType":"semver"},{"version":"6.5.3","status":"unaffected","lessThanOrEqual":"6.5.*","versionType":"semver"},{"version":"6.6","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]}],"references":["https://git.kernel.org/stable/c/791a12102e5191dcb6ce0b3a99d71b5a2802d12a","https://git.kernel.org/stable/c/7dcbc0bb0e5cc1823923744befce59ac353135e6","https://git.kernel.org/stable/c/c0ce0fb76610d5fad31f56f2ca8241a2a6717a1b","https://git.kernel.org/stable/c/8aa43cfbb68b25119d2ced14ec717173e2901fa2","https://git.kernel.org/stable/c/3d4522f59fb748a54446846522941a4f09da63e9","https://git.kernel.org/stable/c/67312adc96b5a585970d03b62412847afe2c6b01"],"weaknesses":[],"ingestedAt":"2026-10-29T20:06:33.064Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2023/53xxx/CVE-2023-53585.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2023-53585","state":"PUBLISHED","datePublished":"2025-10-04T15:44:01.022Z","dateUpdated":"2026-05-11T19:47:54.787Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-10-04T15:40:38.477Z"},"containers":{"cna":{"title":"bpf: reject unhashed sockets in bpf_sk_assign","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: reject unhashed sockets in bpf_sk_assign\n\nThe semantics for bpf_sk_assign are as follows:\n\n    sk = some_lookup_func()\n    bpf_sk_assign(skb, sk)\n    bpf_sk_release(sk)\n\nThat is, the sk is not consumed by bpf_sk_assign. The function\ntherefore needs to make sure that sk lives long enough to be\nconsumed from __inet_lookup_skb. The path through the stack for a\nTCPv4 packet is roughly:\n\n  netif_receive_skb_core: takes RCU read lock\n    __netif_receive_skb_core:\n      sch_handle_ingress:\n        tcf_classify:\n          bpf_sk_assign()\n      deliver_ptype_list_skb:\n        deliver_skb:\n          ip_packet_type->func == ip_rcv:\n            ip_rcv_core:\n            ip_rcv_finish_core:\n              dst_input:\n                ip_local_deliver:\n                  ip_local_deliver_finish:\n                    ip_protocol_deliver_rcu:\n                      tcp_v4_rcv:\n                        __inet_lookup_skb:\n                          skb_steal_sock\n\nThe existing helper takes advantage of the fact that everything\nhappens in the same RCU critical section: for sockets with\nSOCK_RCU_FREE set bpf_sk_assign never takes a reference.\nskb_steal_sock then checks SOCK_RCU_FREE again and does sock_put\nif necessary.\n\nThis approach assumes that SOCK_RCU_FREE is never set on a sk\nbetween bpf_sk_assign and skb_steal_sock, but this invariant is\nviolated by unhashed UDP sockets. A new UDP socket is created\nin TCP_CLOSE state but without SOCK_RCU_FREE set. That flag is only\nadded in udp_lib_get_port() which happens when a socket is bound.\n\nWhen bpf_sk_assign was added it wasn't possible to access unhashed\nUDP sockets from BPF, so this wasn't a problem. This changed\nin commit 0c48eefae712 (\"sock_map: Lift socket state restriction\nfor datagram sockets\"), but the helper wasn't adjusted accordingly.\nThe following sequence of events will therefore lead to a refcount\nleak:\n\n1. Add socket(AF_INET, SOCK_DGRAM) to a sockmap.\n2. Pull socket out of sockmap and bpf_sk_assign it. Since\n   SOCK_RCU_FREE is not set we increment the refcount.\n3. bind() or connect() the socket, setting SOCK_RCU_FREE.\n4. skb_steal_sock will now set refcounted = false due to\n   SOCK_RCU_FREE.\n5. tcp_v4_rcv() skips sock_put().\n\nFix the problem by rejecting unhashed sockets in bpf_sk_assign().\nThis matches the behaviour of __inet_lookup_skb which is ultimately\nthe goal of bpf_sk_assign()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"791a12102e5191dcb6ce0b3a99d71b5a2802d12a","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"7dcbc0bb0e5cc1823923744befce59ac353135e6","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"c0ce0fb76610d5fad31f56f2ca8241a2a6717a1b","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"8aa43cfbb68b25119d2ced14ec717173e2901fa2","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"3d4522f59fb748a54446846522941a4f09da63e9","versionType":"git"},{"version":"cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449","status":"affected","lessThan":"67312adc96b5a585970d03b62412847afe2c6b01","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"5.10.195","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.132","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.53","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.4.16","status":"unaffected","lessThanOrEqual":"6.4.*","versionType":"semver"},{"version":"6.5.3","status":"unaffected","lessThanOrEqual":"6.5.*","versionType":"semver"},{"version":"6.6","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/791a12102e5191dcb6ce0b3a99d71b5a2802d12a"},{"url":"https://git.kernel.org/stable/c/7dcbc0bb0e5cc1823923744befce59ac353135e6"},{"url":"https://git.kernel.org/stable/c/c0ce0fb76610d5fad31f56f2ca8241a2a6717a1b"},{"url":"https://git.kernel.org/stable/c/8aa43cfbb68b25119d2ced14ec717173e2901fa2"},{"url":"https://git.kernel.org/stable/c/3d4522f59fb748a54446846522941a4f09da63e9"},{"url":"https://git.kernel.org/stable/c/67312adc96b5a585970d03b62412847afe2c6b01"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T19:47:54.787Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.10.195"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.15.132"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.1.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.4.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.5.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.6"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}