{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2024-42239 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2024-42239 is a medium-severity vulnerability in Linux kernel, published on 7 Aug 2024. 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-2024-42239 and fix it if it is affected.\n\nWhat it is: CVE-2024-42239 is a medium-severity vulnerability in Linux kernel, published on 7 Aug 2024. 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-2024-42239 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-2024-42239/ (Markdown: https://insights.sbomify.com/CVE-2024-42239/index.md)","id":"CVE-2024-42239","markdown":"https://insights.sbomify.com/CVE-2024-42239/index.md","name":"CVE-2024-42239","record":{"aliases":["AZL-47453","AZL-47604","BELL-CVE-2024-42239","DEBIAN-CVE-2024-42239","GHSA-ggh4-5hvc-554r","ROOT-OS-DEBIAN-12-CVE-2024-42239","ROOT-OS-UBUNTU-2204-CVE-2024-42239","UBUNTU-CVE-2024-42239"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"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 BPF timer cancellation logic can cause a deadlock and system lockup when multiple timers cancel each other.","user_interaction":"not_required","vuln_class":"race_condition"},"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-667","name":"Improper Locking"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fail bpf_timer_cancel when callback is being cancelled\n\nGiven a schedule:\n\ntimer1 cb\t\t\ttimer2 cb\n\nbpf_timer_cancel(timer2);\tbpf_timer_cancel(timer1);\n\nBoth bpf_timer_cancel calls would wait for the other callback to finish\nexecuting, introducing a lockup.\n\nAdd an atomic_t count named 'cancelling' in bpf_hrtimer. This keeps\ntrack of all in-flight cancellation requests for a given BPF timer.\nWhenever cancelling a BPF timer, we must check if we have outstanding\ncancellation requests, and if so, we must fail the operation with an\nerror (-EDEADLK) since cancellation is synchronous and waits for the\ncallback to finish executing. This implies that we can enter a deadlock\nsituation involving two or more timer callbacks executing in parallel\nand attempting to cancel one another.\n\nNote that we avoid incrementing the cancelling counter for the target\ntimer (the one being cancelled) if bpf_timer_cancel is not invoked from\na callback, to avoid spurious errors. The whole point of detecting\ncur-\u003ecancelling and returning -EDEADLK is to not enter a busy wait loop\n(which may or may not lead to a lockup). This does not apply in case the\ncaller is in a non-callback context, the other side can continue to\ncancel as it sees fit without running into errors.\n\nBackground on prior attempts:\n\nEarlier versions of this patch used a bool 'cancelling' bit and used the\nfollowing pattern under timer-\u003elock to publish cancellation status.\n\nlock(t-\u003elock);\nt-\u003ecancelling = true;\nmb();\nif (cur-\u003ecancelling)\n\treturn -EDEADLK;\nunlock(t-\u003elock);\nhrtimer_cancel(t-\u003etimer);\nt-\u003ecancelling = false;\n\nThe store outside the critical section could overwrite a parallel\nrequests t-\u003ecancelling assignment to true, to ensure the parallely\nexecuting callback observes its cancellation status.\n\nIt would be necessary to clear this cancelling bit once hrtimer_cancel\nis done, but lack of serialization introduced races. Another option was\nexplored where bpf_timer_start would clear the bit when (re)starting the\ntimer under timer-\u003elock. This would ensure serialized access to the\ncancelling bit, but may allow it to be cleared before in-flight\nhrtimer_cancel has finished executing, such that lockups can occur\nagain.\n\nThus, we choose an atomic counter to keep track of all outstanding\ncancellation requests and use it to prevent lockups in case callbacks\nattempt to cancel each other while executing in parallel.","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":"bpf: Fail bpf_timer_cancel when callback is being cancelled","id":"CVE-2024-42239","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"race_condition","year":"2024"},"n_packages":0,"n_references":3,"next":{"headline":"x86/bhi: Avoid warning in #DB handler due to BHI mitigation","id":"CVE-2024-42240"},"packages":[],"prev":{"headline":"firmware: cs_dsp: Return error if block header overflows file","id":"CVE-2024-42238"},"products":["Linux"],"published":"2024-08-07","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":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-05-11","vendors":["Linux"]},"summary":"A race condition in the Linux kernel BPF timer cancellation logic can cause a deadlock and system lockup when multiple timers cancel each other.","url":"https://insights.sbomify.com/CVE-2024-42239/"}