{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2025-21813 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2025-21813 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 2025. 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-2025-21813 and fix it if it is affected.\n\nWhat it is: CVE-2025-21813 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 2025. 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-2025-21813 in the wild and no public exploit code.\n\nAffected product: Linux kernel. 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-2025-21813/ (Markdown: https://insights.sbomify.com/CVE-2025-21813/index.md)","id":"CVE-2025-21813","markdown":"https://insights.sbomify.com/CVE-2025-21813/index.md","name":"CVE-2025-21813","record":{"aliases":["BELL-CVE-2025-21813","DEBIAN-CVE-2025-21813","GHSA-xjrx-58mf-555f","UBUNTU-CVE-2025-21813","USN-7489-1","USN-7489-2"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel timer","requires_auth":"low_privilege","summary":"An off-by-one error in Linux kernel timer migration logic can cause incorrect root connections, potentially leading to system instability or warnings.","user_interaction":"not_required","vuln_class":"other"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":5.5,"severity":"medium","source":"nvd","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[{"id":"CWE-193","name":"Off-by-one Error"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntimers/migration: Fix off-by-one root mis-connection\n\nBefore attaching a new root to the old root, the children counter of the\nnew root is checked to verify that only the upcoming CPU's top group have\nbeen connected to it. However since the recently added commit b729cc1ec21a\n(\"timers/migration: Fix another race between hotplug and idle entry/exit\")\nthis check is not valid anymore because the old root is pre-accounted\nas a child to the new root. Therefore after connecting the upcoming\nCPU's top group to the new root, the children count to be expected must\nbe 2 and not 1 anymore.\n\nThis omission results in the old root to not be connected to the new\nroot. Then eventually the system may run with more than one top level,\nwhich defeats the purpose of a single idle migrator.\n\nAlso the old root is pre-accounted but not connected upon the new root\ncreation. But it can be connected to the new root later on. Therefore\nthe old root may be accounted twice to the new root. The propagation of\nsuch overcommit can end up creating a double final top-level root with a\ngroupmask incorrectly initialized. Although harmless given that the final\ntop level roots will never have a parent to walk up to, this oddity\nopportunistically reported the core issue:\n\n  WARNING: CPU: 8 PID: 0 at kernel/time/timer_migration.c:543 tmigr_requires_handle_remote\n  CPU: 8 UID: 0 PID: 0 Comm: swapper/8\n  RIP: 0010:tmigr_requires_handle_remote\n  Call Trace:\n   \u003cIRQ\u003e\n   ? tmigr_requires_handle_remote\n   ? hrtimer_run_queues\n   update_process_times\n   tick_periodic\n   tick_handle_periodic\n   __sysvec_apic_timer_interrupt\n   sysvec_apic_timer_interrupt\n  \u003c/IRQ\u003e\n\nFix the problem by taking the old root into account in the children count\nof the new root so the connection is not omitted.\n\nAlso warn when more than one top level group exists to better detect\nsimilar issues in the future.","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":"timers/migration: Fix off-by-one root mis-connection","id":"CVE-2025-21813","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"other","year":"2025"},"n_packages":0,"n_references":3,"next":{"headline":"ptp: Ensure info-\u003eenable callback is always set","id":"CVE-2025-21814"},"packages":[],"prev":{"headline":"ax25: rcu protect dev-\u003eax25_ptr","id":"CVE-2025-21812"},"products":["Linux"],"published":"2025-02-27","related":[{"cvss_score":8.8,"headline":"Linux Kernel Out-of-Bounds Write","id":"CVE-2026-53266","kev_date_added":"2026-09-18","published":"2026-06-25"},{"cvss_score":8.8,"headline":"Linux Kernel Improper Input Validation","id":"CVE-2013-6282","kev_date_added":"2022-09-15","published":"2013-11-19"},{"cvss_score":8.4,"headline":"Linux Kernel Heap-Based Buffer Overflow","id":"CVE-2022-0185","kev_date_added":"2024-08-21","published":"2022-02-11"},{"cvss_score":8.4,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2013-2094","kev_date_added":"2022-09-15","published":"2013-05-14"},{"cvss_score":7.8,"headline":"Linux Kernel Unspecified","id":"CVE-2026-53362","kev_date_added":"2026-08-27","published":"2026-07-04"},{"cvss_score":7.8,"headline":"Linux Kernel Missing Initialization of a Variable","id":"CVE-2026-46300","kev_date_added":"2026-10-28","published":"2026-05-23"},{"cvss_score":7.8,"headline":"Linux Kernel Race Condition","id":"CVE-2025-39964","kev_date_added":"2026-09-18","published":"2025-10-13"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-05-23","vendors":["Linux"]},"summary":"An off-by-one error in Linux kernel timer migration logic can cause incorrect root connections, potentially leading to system instability or warnings.","url":"https://insights.sbomify.com/CVE-2025-21813/"}