{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-89791 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-89791 is a high-severity use after free vulnerability in Linux, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-89791 and fix it if it is affected.\n\nWhat it is: CVE-2026-89791 is a high-severity use after free vulnerability in Linux, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-89791 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-89791/ (Markdown: https://insights.sbomify.com/CVE-2026-89791/index.md)","id":"CVE-2026-89791","markdown":"https://insights.sbomify.com/CVE-2026-89791/index.md","name":"CVE-2026-89791","record":{"aliases":["BELL-CVE-2026-89791","DEBIAN-CVE-2026-89791","GHSA-3xg9-4g5f-3mp3","UBUNTU-CVE-2026-89791"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["privilege_escalation"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"A race condition in the Linux kernel perf subsystem allows local attackers to trigger a use-after-free, leading to privilege escalation to root.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":7.8,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Fix use-after-free when perf mmap() revival races with the last munmap()\n\nperf_mmap_close() drops rb-\u003emmap_count *without* holding\nevent-\u003emmap_mutex (the refcount_dec_and_test() right before the\nrefcount_dec_and_mutex_lock() of event-\u003emmap_count). A concurrent\nperf_mmap_rb() can slot its entire \"revival\" path into that window\n(perf_mmap holds event-\u003emmap_mutex for its whole duration, including\nrb_alloc):\n\n  munmap side (perf_mmap_close)          mmap side (perf_mmap_rb)\n  -----------------------------------    --------------------------------\n  rb-\u003emmap_count 1 -\u003e 0   (no lock)      (holds event-\u003emmap_mutex)\n                                         inc_not_zero(rb-\u003emmap_count) fails\n                                         ring_buffer_attach(event, NULL)\n                                         rb_alloc() + attach new rb\n                                         refcount_set(\u0026event-\u003emmap_count, 1)\n  lock; event-\u003emmap_count 1 -\u003e 0\n  ring_buffer_attach(event, NULL)\n  ring_buffer_put() -\u003e frees the *new* rb\n\nThe revival's refcount_set(\u0026event-\u003emmap_count, 1) is an invisible\n1 -\u003e 1 write: the close frees the just-revived buffer although the\nother process still has it mapped -- a page-level use-after-free\nallowing local privilege escalation to root by any unprivileged user\n(default kernel.perf_event_paranoid=2).\n\nSwap the order of the two counter updates: event-\u003emmap_count is\ndropped first via refcount_dec_and_mutex_lock(), so its 1 -\u003e 0\ntransition and the ring_buffer_attach() stay serialized with\nperf_mmap(). rb-\u003emmap_count == 0 then implies every event using the\nbuffer is detached already, so the result of the rb-\u003emmap_count drop\ncan gate the remaining teardown directly and detach_rest is no longer\nneeded.\n\nAn earlier fix for this race from Kyle Zeng and David Lee takes\nevent-\u003emmap_mutex around both counter updates [0]; here the not-last\nclose stays lockless.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"perf: Fix use-after-free when perf mmap() revival races with the last munmap()","id":"CVE-2026-89791","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"use_after_free","year":"2026"},"n_packages":0,"n_references":3,"next":{"headline":"ksmbd: prevent out-of-bounds reads in share config responses","id":"CVE-2026-89792"},"packages":[],"prev":{"headline":"ipv6: avoid divide by zero in rt6_multipath_rebalance","id":"CVE-2026-89790"},"products":["Linux"],"published":"2026-09-16","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-10-19","vendors":["Linux"]},"summary":"A race condition in the Linux kernel perf subsystem allows local attackers to trigger a use-after-free, leading to privilege escalation to root.","url":"https://insights.sbomify.com/CVE-2026-89791/"}