CVE-2026-23127 (GCVE-0-2026-23127)

Vulnerability from cvelistv5 – Published: 2026-02-14 15:09 – Updated: 2026-05-11 22:00
VLAI
Title
perf: Fix refcount warning on event->mmap_count increment
Summary
In the Linux kernel, the following vulnerability has been resolved: perf: Fix refcount warning on event->mmap_count increment When calling refcount_inc(&event->mmap_count) inside perf_mmap_rb(), the following warning is triggered: refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 PoC: struct perf_event_attr attr = {0}; int fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0); mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); int victim = syscall(__NR_perf_event_open, &attr, 0, -1, fd, PERF_FLAG_FD_OUTPUT); mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0); This occurs when creating a group member event with the flag PERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing the event triggers the warning. Since the event has copied the output_event in perf_event_set_output(), event->rb is set. As a result, perf_mmap_rb() calls refcount_inc(&event->mmap_count) when event->mmap_count = 0. Disallow the case when event->mmap_count = 0. This also prevents two events from updating the same user_page.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 448f97fba9013ffa13f5dd82febd18836b189499 , < 23c0e4bd93d0b250775162faf456470485ac9fc7 (git)
Affected: 448f97fba9013ffa13f5dd82febd18836b189499 , < d06bf78e55d5159c1b00072e606ab924ffbbad35 (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.8 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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{
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    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/events/core.c"
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          "vendor": "Linux",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Fix refcount warning on event-\u003emmap_count increment\n\nWhen calling refcount_inc(\u0026event-\u003emmap_count) inside perf_mmap_rb(), the\nfollowing warning is triggered:\n\n        refcount_t: addition on 0; use-after-free.\n        WARNING: lib/refcount.c:25\n\nPoC:\n\n    struct perf_event_attr attr = {0};\n    int fd = syscall(__NR_perf_event_open, \u0026attr, 0, -1, -1, 0);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);\n    int victim = syscall(__NR_perf_event_open, \u0026attr, 0, -1, fd,\n                         PERF_FLAG_FD_OUTPUT);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);\n\nThis occurs when creating a group member event with the flag\nPERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing\nthe event triggers the warning.\n\nSince the event has copied the output_event in perf_event_set_output(),\nevent-\u003erb is set. As a result, perf_mmap_rb() calls\nrefcount_inc(\u0026event-\u003emmap_count) when event-\u003emmap_count = 0.\n\nDisallow the case when event-\u003emmap_count = 0. This also prevents two\nevents from updating the same user_page."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:00:39.060Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/23c0e4bd93d0b250775162faf456470485ac9fc7"
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          "url": "https://git.kernel.org/stable/c/d06bf78e55d5159c1b00072e606ab924ffbbad35"
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    "assignerShortName": "Linux",
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    "datePublished": "2026-02-14T15:09:56.237Z",
    "dateReserved": "2026-01-13T15:37:45.970Z",
    "dateUpdated": "2026-05-11T22:00:39.060Z",
    "state": "PUBLISHED"
  },
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    "epss": {
      "cve": "CVE-2026-23127",
      "date": "2026-05-25",
      "epss": "0.00019",
      "percentile": "0.05526"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23127\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-02-14T15:16:07.963\",\"lastModified\":\"2026-03-18T14:49:58.400\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nperf: Fix refcount warning on event-\u003emmap_count increment\\n\\nWhen calling refcount_inc(\u0026event-\u003emmap_count) inside perf_mmap_rb(), the\\nfollowing warning is triggered:\\n\\n        refcount_t: addition on 0; use-after-free.\\n        WARNING: lib/refcount.c:25\\n\\nPoC:\\n\\n    struct perf_event_attr attr = {0};\\n    int fd = syscall(__NR_perf_event_open, \u0026attr, 0, -1, -1, 0);\\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);\\n    int victim = syscall(__NR_perf_event_open, \u0026attr, 0, -1, fd,\\n                         PERF_FLAG_FD_OUTPUT);\\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);\\n\\nThis occurs when creating a group member event with the flag\\nPERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing\\nthe event triggers the warning.\\n\\nSince the event has copied the output_event in perf_event_set_output(),\\nevent-\u003erb is set. As a result, perf_mmap_rb() calls\\nrefcount_inc(\u0026event-\u003emmap_count) when event-\u003emmap_count = 0.\\n\\nDisallow the case when event-\u003emmap_count = 0. This also prevents two\\nevents from updating the same user_page.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nperf: Correcci\u00f3n de la advertencia de refcount en el incremento de event-\u0026gt;mmap_count\\n\\nAl llamar a refcount_inc(\u0026amp;event-\u0026gt;mmap_count) dentro de perf_mmap_rb(), se activa la siguiente advertencia:\\n\\n        refcount_t: adici\u00f3n en 0; uso despu\u00e9s de liberaci\u00f3n.\\n        ADVERTENCIA: lib/refcount.c:25\\n\\nPoC:\\n\\n    struct perf_event_attr attr = {0};\\n    int fd = syscall(__NR_perf_event_open, \u0026amp;attr, 0, -1, -1, 0);\\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);\\n    int victim = syscall(__NR_perf_event_open, \u0026amp;attr, 0, -1, fd,\\n                         PERF_FLAG_FD_OUTPUT);\\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);\\n\\nEsto ocurre al crear un evento miembro de grupo con la bandera PERF_FLAG_FD_OUTPUT. El l\u00edder del grupo debe ser mapeado con mmap y luego mapear el evento con mmap activa la advertencia.\\n\\nDado que el evento ha copiado el output_event en perf_event_set_output(), event-\u0026gt;rb est\u00e1 establecido. Como resultado, perf_mmap_rb() llama a refcount_inc(\u0026amp;event-\u0026gt;mmap_count) cuando event-\u0026gt;mmap_count = 0.\\n\\nNo permitir el caso cuando event-\u0026gt;mmap_count = 0. Esto tambi\u00e9n evita que dos eventos actualicen la misma user_page.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":5.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"NVD-CWE-Other\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.18\",\"versionEndExcluding\":\"6.18.8\",\"matchCriteriaId\":\"7B26C1E1-97A9-48B8-81C6-B6A3A0FC6C7E\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"17B67AA7-40D6-4AFA-8459-F200F3D7CFD1\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"C47E4CC9-C826-4FA9-B014-7FE3D9B318B2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"F71D92C0-C023-48BD-B3B6-70B638EEE298\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"13580667-0A98-40CC-B29F-D12790B91BDB\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"CAD1FED7-CF48-47BF-AC7D-7B6FA3C065FC\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.19:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"3EF854A1-ABB1-4E93-BE9A-44569EC76C0D\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/23c0e4bd93d0b250775162faf456470485ac9fc7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/d06bf78e55d5159c1b00072e606ab924ffbbad35\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}"
  }
}


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