{"cve":"CVE-2026-23127","nvd":{"published":"2026-02-14T15:16:07.963","modified":"2026-06-17T10:20:56.943","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Fix refcount warning on event->mmap_count increment\n\nWhen calling refcount_inc(&event->mmap_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, &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, &attr, 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->rb is set. As a result, perf_mmap_rb() calls\nrefcount_inc(&event->mmap_count) when event->mmap_count = 0.\n\nDisallow the case when event->mmap_count = 0. This also prevents two\nevents from updating the same user_page.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/23c0e4bd93d0b250775162faf456470485ac9fc7","https://git.kernel.org/stable/c/d06bf78e55d5159c1b00072e606ab924ffbbad35"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:23:35.260773158+00:00"},"epss":{"cve":"CVE-2026-23127","score":0.00117,"percentile":0.01659,"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."]}