{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2023-53781",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2025-12-08T23:58:35.272Z",
        "datePublished": "2025-12-09T00:00:36.831Z",
        "dateUpdated": "2026-08-05T09:15:58.590Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T09:15:58.590Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmc: Fix use-after-free in tcp_write_timer_handler().\n\nWith Eric's ref tracker, syzbot finally found a repro for\nuse-after-free in tcp_write_timer_handler() by kernel TCP\nsockets. [0]\n\nIf SMC creates a kernel socket in __smc_create(), the kernel\nsocket is supposed to be freed in smc_clcsock_release() by\ncalling sock_release() when we close() the parent SMC socket.\n\nHowever, at the end of smc_clcsock_release(), the kernel\nsocket's sk_state might not be TCP_CLOSE.  This means that\nwe have not called inet_csk_destroy_sock() in __tcp_close()\nand have not stopped the TCP timers.\n\nThe kernel socket's TCP timers can be fired later, so we\nneed to hold a refcnt for net as we do for MPTCP subflows\nin mptcp_subflow_create_socket().\n\n[0]:\nleaked reference.\n sk_alloc (./include/net/net_namespace.h:335 net/core/sock.c:2108)\n inet_create (net/ipv4/af_inet.c:319 net/ipv4/af_inet.c:244)\n __sock_create (net/socket.c:1546)\n smc_create (net/smc/af_smc.c:3269 net/smc/af_smc.c:3284)\n __sock_create (net/socket.c:1546)\n __sys_socket (net/socket.c:1634 net/socket.c:1618 net/socket.c:1661)\n __x64_sys_socket (net/socket.c:1672)\n do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)\n==================================================================\nBUG: KASAN: slab-use-after-free in tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594)\nRead of size 1 at addr ffff888052b65e0d by task syzrepro/18091\n\nCPU: 0 PID: 18091 Comm: syzrepro Tainted: G        W          6.3.0-rc4-01174-gb5d54eb5899a #7\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014\nCall Trace:\n <IRQ>\n dump_stack_lvl (lib/dump_stack.c:107)\n print_report (mm/kasan/report.c:320 mm/kasan/report.c:430)\n kasan_report (mm/kasan/report.c:538)\n tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594)\n tcp_write_timer (./include/linux/spinlock.h:390 net/ipv4/tcp_timer.c:643)\n call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701)\n __run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2022)\n run_timer_softirq (kernel/time/timer.c:2037)\n __do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:572)\n __irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650)\n irq_exit_rcu (kernel/softirq.c:664)\n sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1107 (discriminator 14))\n </IRQ>"
                }
            ],
            "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 - The UAF is triggered by a locally-armed TCP timer; the attacker reaches it entirely through local syscalls (creating an AF_SMC socket, connecting it, closing it) plus network-namespace teardown. No received network packet triggers the vulnerable code path, so this is a local attack surface.\nAC:L - The attacker controls both sides: they arm the clcsock's TCP timers (e.g. connecting to an unresponsive peer so it stays non-TCP_CLOSE) and control when the net namespace is destroyed, and can spray many socket/namespace pairs to reliably land the timer firing on freed memory.\nPR:L - Triggering requires a destroyable network namespace (the init netns is never freed), which an unprivileged local user obtains via user namespaces (unshare -Urn); AF_SMC socket creation itself is not capability-gated.\nUI:N - The attacker performs all setup (socket creation, connect, close, namespace teardown) themselves; no victim action is required.\nS:U - The use-after-free corrupts a freed struct net within the kernel's own security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:H - This is a slab use-after-free of struct net whose freed memory can be reclaimed with attacker-influenced data before the timer reads sysctl fields from it, enabling information disclosure per UAF guidance.\nI:H - The timer handlers write into the freed net object (MIB counter increments via __NET_INC_STATS), and reclaiming the freed slab enables heap-spray/write primitives, so integrity impact is High per UAF guidance.\nA:H - A use-after-free of the network namespace reliably causes kernel oops/panic (as reported by KASAN/syzbot), giving High availability impact."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/smc/af_smc.c"
                    ],
                    "versions": [
                        {
                            "version": "ac7138746e14137a451f8539614cdd349153e0c0",
                            "lessThan": "1cc41c8acfc1ee30b4868559058db97fa44b0137",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "ac7138746e14137a451f8539614cdd349153e0c0",
                            "lessThan": "9744d2bf19762703704ecba885b7ac282c02eacf",
                            "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/af_smc.c"
                    ],
                    "versions": [
                        {
                            "version": "4.11",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "4.11",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.2.12",
                            "lessThanOrEqual": "6.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.3",
                            "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": "6.2.12"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "4.11",
                                    "versionEndExcluding": "6.3"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/1cc41c8acfc1ee30b4868559058db97fa44b0137"
                },
                {
                    "url": "https://git.kernel.org/stable/c/9744d2bf19762703704ecba885b7ac282c02eacf"
                }
            ],
            "title": "smc: Fix use-after-free in tcp_write_timer_handler().",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}