Vulnerability-Lookup

CVE-2023-53781 (GCVE-0-2023-53781)

Vulnerability from cvelistv5 – Published: 2025-12-09 00:00 – Updated: 2026-08-05 09:15

Title

smc: Fix use-after-free in tcp_write_timer_handler().

Summary

In the Linux kernel, the following vulnerability has been resolved: smc: Fix use-after-free in tcp_write_timer_handler(). With Eric's ref tracker, syzbot finally found a repro for use-after-free in tcp_write_timer_handler() by kernel TCP sockets. [0] If SMC creates a kernel socket in __smc_create(), the kernel socket is supposed to be freed in smc_clcsock_release() by calling sock_release() when we close() the parent SMC socket. However, at the end of smc_clcsock_release(), the kernel socket's sk_state might not be TCP_CLOSE. This means that we have not called inet_csk_destroy_sock() in __tcp_close() and have not stopped the TCP timers. The kernel socket's TCP timers can be fired later, so we need to hold a refcnt for net as we do for MPTCP subflows in mptcp_subflow_create_socket(). [0]: leaked reference. sk_alloc (./include/net/net_namespace.h:335 net/core/sock.c:2108) inet_create (net/ipv4/af_inet.c:319 net/ipv4/af_inet.c:244) __sock_create (net/socket.c:1546) smc_create (net/smc/af_smc.c:3269 net/smc/af_smc.c:3284) __sock_create (net/socket.c:1546) __sys_socket (net/socket.c:1634 net/socket.c:1618 net/socket.c:1661) __x64_sys_socket (net/socket.c:1672) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) ================================================================== BUG: 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) Read of size 1 at addr ffff888052b65e0d by task syzrepro/18091 CPU: 0 PID: 18091 Comm: syzrepro Tainted: G W 6.3.0-rc4-01174-gb5d54eb5899a #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:107) print_report (mm/kasan/report.c:320 mm/kasan/report.c:430) kasan_report (mm/kasan/report.c:538) tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594) tcp_write_timer (./include/linux/spinlock.h:390 net/ipv4/tcp_timer.c:643) 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) __run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2022) run_timer_softirq (kernel/time/timer.c:2037) __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) __irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650) irq_exit_rcu (kernel/softirq.c:664) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1107 (discriminator 14)) </IRQ>

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/1cc41c8acfc1ee30b…
https://git.kernel.org/stable/c/9744d2bf197627037…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: ac7138746e14137a451f8539614cdd349153e0c0 , < 1cc41c8acfc1ee30b4868559058db97fa44b0137 (git) Affected: ac7138746e14137a451f8539614cdd349153e0c0 , < 9744d2bf19762703704ecba885b7ac282c02eacf (git)	guessed
Linux	Linux	Affected: 4.11 Unaffected: 0 , < 4.11 (semver) Unaffected: 6.2.12 , ≤ 6.2.* (semver) Unaffected: 6.3 , ≤ * (original_commit_for_fix)	guessed

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/smc/af_smc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1cc41c8acfc1ee30b4868559058db97fa44b0137",
              "status": "affected",
              "version": "ac7138746e14137a451f8539614cdd349153e0c0",
              "versionType": "git"
            },
            {
              "lessThan": "9744d2bf19762703704ecba885b7ac282c02eacf",
              "status": "affected",
              "version": "ac7138746e14137a451f8539614cdd349153e0c0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/smc/af_smc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.11"
            },
            {
              "lessThan": "4.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.2.*",
              "status": "unaffected",
              "version": "6.2.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.2.12",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.3",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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\u0027s 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\u0027s 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\u0027s 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 \u003cIRQ\u003e\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 \u003c/IRQ\u003e"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "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\u0027s 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\u0027s 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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:15:58.590Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53781",
    "datePublished": "2025-12-09T00:00:36.831Z",
    "dateReserved": "2025-12-08T23:58:35.272Z",
    "dateUpdated": "2026-08-05T09:15:58.590Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2023-53781",
      "date": "2026-09-17",
      "epss": "0.00144",
      "percentile": "0.04086"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2023-53781\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-09T01:16:49.280\",\"lastModified\":\"2026-08-04T10:19:21.043\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"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\u0027s 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\u0027s 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\u0027s 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 \u003cIRQ\u003e\\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 \u003c/IRQ\u003e\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/smc/af_smc.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"ac7138746e14137a451f8539614cdd349153e0c0\",\"lessThan\":\"1cc41c8acfc1ee30b4868559058db97fa44b0137\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ac7138746e14137a451f8539614cdd349153e0c0\",\"lessThan\":\"9744d2bf19762703704ecba885b7ac282c02eacf\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/smc/af_smc.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.11\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.11\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.2.12\",\"lessThanOrEqual\":\"6.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.3\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1cc41c8acfc1ee30b4868559058db97fa44b0137\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9744d2bf19762703704ecba885b7ac282c02eacf\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:16:15+00:00",
      "cve": "CVE-2023-53781",
      "id": "CVE-2023-53781",
      "initial_release_date": "2023-01-01T00:00:00+00:00",
      "product_status:fixed": "453",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "118",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smc: Fix use-after-free in tcp_write_timer_handler()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-53781.json",
      "version": "3"
    }
  }
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2023-53781 (GCVE-0-2023-53781)

Tags

Sightings

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Related by attack behaviour