{"cve":"CVE-2025-38563","nvd":{"published":"2025-08-19T17:15:32.790","modified":"2026-06-17T09:17:07.083","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Prevent VMA split of buffer mappings\n\nThe perf mmap code is careful about mmap()'ing the user page with the\nringbuffer and additionally the auxiliary buffer, when the event supports\nit. Once the first mapping is established, subsequent mapping have to use\nthe same offset and the same size in both cases. The reference counting for\nthe ringbuffer and the auxiliary buffer depends on this being correct.\n\nThough perf does not prevent that a related mapping is split via mmap(2),\nmunmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls,\nwhich take reference counts, but then the subsequent perf_mmap_close()\ncalls are not longer fulfilling the offset and size checks. This leads to\nreference count leaks.\n\nAs perf already has the requirement for subsequent mappings to match the\ninitial mapping, the obvious consequence is that VMA splits, caused by\nresizing of a mapping or partial unmapping, have to be prevented.\n\nImplement the vm_operations_struct::may_split() callback and return\nunconditionally -EINVAL.\n\nThat ensures that the mapping offsets and sizes cannot be changed after the\nfact. Remapping to a different fixed address with the same size is still\npossible as it takes the references for the new mapping and drops those of\nthe old mapping.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":[],"references":["https://git.kernel.org/stable/c/3bd518cc7ea61076bcd725e36ff0e690754977c0","https://git.kernel.org/stable/c/65311aad4c808bedad0c05d9bb8b06c47dae73eb","https://git.kernel.org/stable/c/6757a31a8e295ae4f01717a954afda173f25a121","https://git.kernel.org/stable/c/7b84cb58d1f0aa07656802eae24689566e5f5b1b","https://git.kernel.org/stable/c/b024d7b56c77191cde544f838debb7f8451cd0d6"],"products":["debian:debian_linux","linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:06:45.861874017+00:00"},"epss":{"cve":"CVE-2025-38563","score":0.00403,"percentile":0.34572,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}