{"id":"CVE-2026-23248","title":"perf/core: Fix refcount bug and potential UAF in perf_mmap","summary":"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…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < c27dea9f50ed525facb62ef647dddc4722456e07","Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < ac7ecb65af170a7fc193e7bd8be15dac84ec6a56","Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < 77de62ad3de3967818c3dbe656b7336ebee461d2","Linux 6.14"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:06:58.307161Z"},"published":"2026-03-18","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:09:51.119Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23248","references":[{"url":"https://git.kernel.org/stable/c/c27dea9f50ed525facb62ef647dddc4722456e07"},{"url":"https://git.kernel.org/stable/c/ac7ecb65af170a7fc193e7bd8be15dac84ec6a56"},{"url":"https://git.kernel.org/stable/c/77de62ad3de3967818c3dbe656b7336ebee461d2"}],"tags":["cve.org"],"epss":0.00124,"epssPercentile":0.01928,"ingestedAt":"2026-10-16T17:24:46.642Z","slug":"CVE-2026-23248","body":"## Overview\n\nIn 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->rb 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->rb 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.\n\n## Affected\n\n- `Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < c27dea9f50ed525facb62ef647dddc4722456e07`\n- `Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < ac7ecb65af170a7fc193e7bd8be15dac84ec6a56`\n- `Linux >= b709eb872e19a19607bbb6d2975bc264d59735cf < 77de62ad3de3967818c3dbe656b7336ebee461d2`\n- `Linux 6.14`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}