CVE-2026-74633 (GCVE-0-2026-74633)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-22 15:32
VLAI
Title
tracing: Fix NULL pointer dereference in module event cache removal
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix NULL pointer dereference in module event cache removal A module-only event filter such as ":mod:foo" is cached with a NULL event_mod->match when foo has not been loaded. If a later write tries to remove a specific match from the same module, remove_cache_mod() passes the NULL cached match to strcmp(), causing a NULL pointer dereference. The issue can be reproduced from userspace: echo ':mod:trace_events_kunit_missing' > /sys/kernel/tracing/set_event echo '!foo_bar:mod:trace_events_kunit_missing' >> /sys/kernel/tracing/set_event The second write must be a concatenation (">>") to not include O_TRUNC as that would cause ftrace_clear_events() to clear the cached modules lines. The crash was reproduced on x86_64 QEMU while KUnit workers contended on the event tracing path: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode RIP: 0010:strcmp+0x10/0x30 Call Trace: __ftrace_set_clr_event_nolock+0x373/0x4a0 ftrace_set_clr_event+0xf0/0x180 ftrace_event_write+0xdf/0x110 vfs_write+0xf6/0x440 ksys_write+0x68/0xe0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Check event_mod->match before comparing it, consistent with the existing NULL checks for the cached system and event fields. The mismatched removal continues to return -EINVAL; a broad cached module filter is removed with "!:mod:<module>".
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6664 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b355247df104ef6644288884afd2c08b7bf49897 , < 152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9 (git)
Affected: b355247df104ef6644288884afd2c08b7bf49897 , < ad4e9dd5fec7a322a471ff36fb9c76214e3c6992 (git)
Affected: b355247df104ef6644288884afd2c08b7bf49897 , < b69859204d4db3acd86c1c2dadcef0d77b451933 (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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        {
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          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_events.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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          "versions": [
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              "version": "6.14"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "versionType": "semver"
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              "versionType": "semver"
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              "versionType": "original_commit_for_fix"
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                  "versionStartIncluding": "6.14",
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                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix NULL pointer dereference in module event cache removal\n\nA module-only event filter such as \":mod:foo\" is cached with a NULL\nevent_mod-\u003ematch when foo has not been loaded. If a later write tries to\nremove a specific match from the same module, remove_cache_mod() passes\nthe NULL cached match to strcmp(), causing a NULL pointer dereference.\n\nThe issue can be reproduced from userspace:\n\n  echo \u0027:mod:trace_events_kunit_missing\u0027 \u003e /sys/kernel/tracing/set_event\n  echo \u0027!foo_bar:mod:trace_events_kunit_missing\u0027 \u003e\u003e /sys/kernel/tracing/set_event\n\nThe second write must be a concatenation (\"\u003e\u003e\") to not include O_TRUNC as\nthat would cause ftrace_clear_events() to clear the cached modules lines.\n\nThe crash was reproduced on x86_64 QEMU while KUnit workers contended on\nthe event tracing path:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000000\n  #PF: supervisor read access in kernel mode\n  RIP: 0010:strcmp+0x10/0x30\n  Call Trace:\n   __ftrace_set_clr_event_nolock+0x373/0x4a0\n   ftrace_set_clr_event+0xf0/0x180\n   ftrace_event_write+0xdf/0x110\n   vfs_write+0xf6/0x440\n   ksys_write+0x68/0xe0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nCheck event_mod-\u003ematch before comparing it, consistent with the existing\nNULL checks for the cached system and event fields. The mismatched removal\ncontinues to return -EINVAL; a broad cached module filter is removed with\n\"!:mod:\u003cmodule\u003e\"."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-22T15:32:13.808Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9"
        },
        {
          "url": "https://git.kernel.org/stable/c/ad4e9dd5fec7a322a471ff36fb9c76214e3c6992"
        },
        {
          "url": "https://git.kernel.org/stable/c/b69859204d4db3acd86c1c2dadcef0d77b451933"
        }
      ],
      "title": "tracing: Fix NULL pointer dereference in module event cache removal",
      "x_generator": {
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      }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74633",
    "datePublished": "2026-08-22T15:32:13.808Z",
    "dateReserved": "2026-08-15T05:44:03.922Z",
    "dateUpdated": "2026-08-22T15:32:13.808Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74633",
      "date": "2026-10-16",
      "epss": "0.00206",
      "percentile": "0.09968"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "kernel/trace/trace_events.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
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                    "lessThan": "152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9",
                    "status": "affected",
                    "version": "b355247df104ef6644288884afd2c08b7bf49897",
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                  {
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                    "status": "affected",
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                  {
                    "lessThan": "b69859204d4db3acd86c1c2dadcef0d77b451933",
                    "status": "affected",
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                    "versionType": "git"
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                "product": "Linux",
                "programFiles": [
                  "kernel/trace/trace_events.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "6.14"
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                    "version": "0",
                    "versionType": "semver"
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                    "version": "6.18.45",
                    "versionType": "semver"
                  },
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                    "status": "unaffected",
                    "version": "7.1.9",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
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                    "versionType": "original_commit_for_fix"
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              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix NULL pointer dereference in module event cache removal\n\nA module-only event filter such as \":mod:foo\" is cached with a NULL\nevent_mod-\u003ematch when foo has not been loaded. If a later write tries to\nremove a specific match from the same module, remove_cache_mod() passes\nthe NULL cached match to strcmp(), causing a NULL pointer dereference.\n\nThe issue can be reproduced from userspace:\n\n  echo \u0027:mod:trace_events_kunit_missing\u0027 \u003e /sys/kernel/tracing/set_event\n  echo \u0027!foo_bar:mod:trace_events_kunit_missing\u0027 \u003e\u003e /sys/kernel/tracing/set_event\n\nThe second write must be a concatenation (\"\u003e\u003e\") to not include O_TRUNC as\nthat would cause ftrace_clear_events() to clear the cached modules lines.\n\nThe crash was reproduced on x86_64 QEMU while KUnit workers contended on\nthe event tracing path:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000000\n  #PF: supervisor read access in kernel mode\n  RIP: 0010:strcmp+0x10/0x30\n  Call Trace:\n   __ftrace_set_clr_event_nolock+0x373/0x4a0\n   ftrace_set_clr_event+0xf0/0x180\n   ftrace_event_write+0xdf/0x110\n   vfs_write+0xf6/0x440\n   ksys_write+0x68/0xe0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nCheck event_mod-\u003ematch before comparing it, consistent with the existing\nNULL checks for the cached system and event fields. The mismatched removal\ncontinues to return -EINVAL; a broad cached module filter is removed with\n\"!:mod:\u003cmodule\u003e\"."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ntracing: Correcci\u00f3n de desreferencia de puntero NULL en la eliminaci\u00f3n de la cach\u00e9 de eventos de m\u00f3dulo\n\nUn filtro de eventos solo de m\u00f3dulo como \u0027:mod:foo\u0027 se almacena en cach\u00e9 con un event_mod -\u003e match NULL cuando foo no ha sido cargado. Si una escritura posterior intenta eliminar una coincidencia espec\u00edfica del mismo m\u00f3dulo, remove_cache_mod() pasa la coincidencia NULL almacenada en cach\u00e9 a strcmp(), causando una desreferencia de puntero NULL.\n\nEl problema puede reproducirse desde userspace:\n\n  echo \u0027:mod:trace_events_kunit_missing\u0027 \u003e /sys/kernel/tracing/set_event\n  echo \u0027!foo_bar:mod:trace_events_kunit_missing\u0027 \u003e\u003e /sys/kernel/tracing/set_event\n\nLa segunda escritura debe ser una concatenaci\u00f3n (\u0027\u003e\u003e\u0027) para no incluir O_TRUNC, ya que eso har\u00eda que ftrace_clear_events() borrara las l\u00edneas de m\u00f3dulos en cach\u00e9.\n\nEl fallo se reprodujo en x86_64 QEMU mientras los workers de KUnit compet\u00edan en la ruta de rastreo de eventos:\n\n  BUG: desreferencia de puntero NULL del kernel, direcci\u00f3n: 0000000000000000\n  #PF: acceso de lectura de supervisor en modo kernel\n  RIP: 0010:strcmp+0x10/0x30\n  Traza de Llamada:\n   __ftrace_set_clr_event_nolock+0x373/0x4a0\n   ftrace_set_clr_event+0xf0/0x180\n   ftrace_event_write+0xdf/0x110\n   vfs_write+0xf6/0x440\n   ksys_write+0x68/0xe0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nVerificar event_mod -\u003e match antes de compararlo, consistente con las comprobaciones NULL existentes para los campos de sistema y evento en cach\u00e9. La eliminaci\u00f3n no coincidente contin\u00faa devolviendo -EINVAL; un filtro de m\u00f3dulo en cach\u00e9 amplio se elimina con \u0027!:mod:\u003cmodule\u003e\u0027."
          }
        ],
        "id": "CVE-2026-74633",
        "lastModified": "2026-10-14T13:10:00.187",
        "metrics": {},
        "published": "2026-08-22T16:16:36.380",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/152a00440dc6ef62c6e4cf9bd881a7e6bb81fda9"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ad4e9dd5fec7a322a471ff36fb9c76214e3c6992"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-25T10:02:36+00:00",
      "cve": "CVE-2026-74633",
      "id": "CVE-2026-74633",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "14",
      "product_status:known_not_affected": "260",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tracing: Fix NULL pointer dereference in module event cache removal",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74633.json",
      "version": "3"
    }
  }
}



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