CVE-2026-23248 (GCVE-0-2026-23248)

Vulnerability from cvelistv5 – Published: 2026-03-18 10:05 – Updated: 2026-08-05 12:20
VLAI
Title
perf/core: Fix refcount bug and potential UAF in perf_mmap
Summary
In the Linux kernel, the following vulnerability has been resolved: perf/core: Fix refcount bug and potential UAF in perf_mmap Syzkaller reported a refcount_t: addition on 0; use-after-free warning in perf_mmap. The issue is caused by a race condition between a failing mmap() setup and a concurrent mmap() on a dependent event (e.g., using output redirection). In perf_mmap(), the ring_buffer (rb) is allocated and assigned to event->rb with the mmap_mutex held. The mutex is then released to perform map_range(). If map_range() fails, perf_mmap_close() is called to clean up. However, since the mutex was dropped, another thread attaching to this event (via inherited events or output redirection) can acquire the mutex, observe the valid event->rb pointer, and attempt to increment its reference count. If the cleanup path has already dropped the reference count to zero, this results in a use-after-free or refcount saturation warning. Fix this by extending the scope of mmap_mutex to cover the map_range() call. This ensures that the ring buffer initialization and mapping (or cleanup on failure) happens atomically effectively, preventing other threads from accessing a half-initialized or dying ring buffer.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b709eb872e19a19607bbb6d2975bc264d59735cf , < c27dea9f50ed525facb62ef647dddc4722456e07 (git)
Affected: b709eb872e19a19607bbb6d2975bc264d59735cf , < ac7ecb65af170a7fc193e7bd8be15dac84ec6a56 (git)
Affected: b709eb872e19a19607bbb6d2975bc264d59735cf , < 77de62ad3de3967818c3dbe656b7336ebee461d2 (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - The vulnerability is triggered via the perf_event_open() syscall followed by mmap() on the resulting file descriptor, requiring local system access.\nAC:L - The attacker controls both sides of the race by spawning two threads that concurrently mmap() the same perf event fd. Per CVSS guidance, attacker-controlled races are AC:L.\nPR:L - Unprivileged local users can use perf_event_open() with exclude_kernel=1 and per-task events (cpu=-1) even with the default perf_event_paranoid=2, then mmap() the resulting fd to trigger the race.\nUI:N - No user interaction is needed; the attacker creates the perf event and triggers the race entirely on their own.\nS:U - This is a standard kernel use-after-free for privilege escalation within the same security authority; no VM escape or sandbox boundary crossing occurs.\nC:H - The UAF on the perf_buffer heap object allows the attacker to spray controlled data into the freed slab, enabling arbitrary kernel memory reads through the buffer\u0027s data page pointers and user_page.\nI:H - The freed perf_buffer contains function pointers (free_aux) and is accessed through multiple code paths, enabling heap spraying for arbitrary write primitives and control flow hijacking.\nA:H - The use-after-free reliably causes kernel crashes (refcount saturation warnings, oops, or panic) when the freed ring buffer is accessed."
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix refcount bug and potential UAF in perf_mmap\n\nSyzkaller reported a refcount_t: addition on 0; use-after-free warning\nin perf_mmap.\n\nThe issue is caused by a race condition between a failing mmap() setup\nand a concurrent mmap() on a dependent event (e.g., using output\nredirection).\n\nIn perf_mmap(), the ring_buffer (rb) is allocated and assigned to\nevent-\u003erb with the mmap_mutex held. The mutex is then released to\nperform map_range().\n\nIf map_range() fails, perf_mmap_close() is called to clean up.\nHowever, since the mutex was dropped, another thread attaching to\nthis event (via inherited events or output redirection) can acquire\nthe mutex, observe the valid event-\u003erb pointer, and attempt to\nincrement its reference count. If the cleanup path has already\ndropped the reference count to zero, this results in a\nuse-after-free or refcount saturation warning.\n\nFix this by extending the scope of mmap_mutex to cover the\nmap_range() call. This ensures that the ring buffer initialization\nand mapping (or cleanup on failure) happens atomically effectively,\npreventing other threads from accessing a half-initialized or\ndying ring buffer."
          },
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nperf/core: Correcci\u00f3n de error de conteo de referencias y potencial UAF en perf_mmap\n\nSyzkaller inform\u00f3 una advertencia de refcount_t: adici\u00f3n en 0; uso despu\u00e9s de liberaci\u00f3n en perf_mmap.\n\nEl problema es causado por una condici\u00f3n de carrera entre una configuraci\u00f3n de mmap() fallida y un mmap() concurrente en un evento dependiente (por ejemplo, usando redirecci\u00f3n de salida).\n\nEn perf_mmap(), el ring_buffer (rb) se asigna y se establece en event-\u0026gt;rb con el mmap_mutex retenido. El mutex es entonces liberado para realizar map_range().\n\nSi map_range() falla, se llama a perf_mmap_close() para limpiar. Sin embargo, dado que el mutex fue liberado, otro hilo que se adjunta a este evento (a trav\u00e9s de eventos heredados o redirecci\u00f3n de salida) puede adquirir el mutex, observar el puntero event-\u0026gt;rb v\u00e1lido e intentar incrementar su conteo de referencias. Si la ruta de limpieza ya ha reducido el conteo de referencias a cero, esto resulta en un uso despu\u00e9s de liberaci\u00f3n o una advertencia de saturaci\u00f3n de conteo de referencias.\n\nEsto se corrige al extender el alcance de mmap_mutex para cubrir la llamada a map_range(). Esto asegura que la inicializaci\u00f3n y el mapeo del b\u00fafer de anillo (o la limpieza en caso de fallo) ocurra de manera at\u00f3mica y efectiva, evitando que otros hilos accedan a un b\u00fafer de anillo medio inicializado o en proceso de terminaci\u00f3n."
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        "id": "CVE-2026-23248",
        "lastModified": "2026-06-17T10:21:11.000",
        "metrics": {
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        "vulnStatus": "Analyzed",
        "weaknesses": [
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              {
                "lang": "en",
                "value": "CWE-416"
              }
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            "source": "nvd@nist.gov",
            "type": "Primary"
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      "current_release_date": "2026-07-02T17:12:20+00:00",
      "cve": "CVE-2026-23248",
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      "initial_release_date": "2026-03-18T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: perf/core: Fix refcount bug and potential UAF in perf_mmap",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23248.json",
      "version": "3"
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}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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