{"id":"CVE-2026-23248","state":"PUBLISHED","title":"perf/core: Fix refcount bug and potential UAF in perf_mmap","description":"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->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.","publishedAt":"2026-03-18T10:05:10.070Z","updatedAt":"2026-10-19T18:35:40.258Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"c27dea9f50ed525facb62ef647dddc4722456e07","versionType":"git"},{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"ac7ecb65af170a7fc193e7bd8be15dac84ec6a56","versionType":"git"},{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"77de62ad3de3967818c3dbe656b7336ebee461d2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/events/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.7","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/events/core.c"]}],"references":["https://git.kernel.org/stable/c/c27dea9f50ed525facb62ef647dddc4722456e07","https://git.kernel.org/stable/c/ac7ecb65af170a7fc193e7bd8be15dac84ec6a56","https://git.kernel.org/stable/c/77de62ad3de3967818c3dbe656b7336ebee461d2"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23248.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23248","state":"PUBLISHED","datePublished":"2026-03-18T10:05:10.070Z","dateUpdated":"2026-10-19T18:35:40.258Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:45.989Z"},"containers":{"cna":{"title":"perf/core: Fix refcount bug and potential UAF in perf_mmap","descriptions":[{"lang":"en","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->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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"c27dea9f50ed525facb62ef647dddc4722456e07","versionType":"git"},{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"ac7ecb65af170a7fc193e7bd8be15dac84ec6a56","versionType":"git"},{"version":"b709eb872e19a19607bbb6d2975bc264d59735cf","status":"affected","lessThan":"77de62ad3de3967818c3dbe656b7336ebee461d2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/events/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.7","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/events/core.c"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","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's 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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:20:56.308Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.17"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.19.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23248","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:06:58.307161Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:40.258Z"}}]}}}