{
  "cveId": "CVE-2026-23248",
  "url": "https://patchblox.com/security/cve/CVE-2026-23248",
  "summary": "CVE-2026-23248 is fixed in 36 products on 1 platform, first by DEBIAN-CVE-2026-23248, released March 18, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "perf/core: Fix refcount bug and potential UAF in perf_mmap",
  "description": "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-\u003Erb 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-\u003Erb 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.",
  "published": "2026-03-18T11:16:16Z",
  "severity": "Moderate",
  "cvss": 7.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.00131,
  "epssPercentile": 0.02748,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23248",
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