{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-47396 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-47396 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 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-2021-47396 and fix it if it is affected.\n\nWhat it is: CVE-2021-47396 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 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-2021-47396 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-2021-47396/ (Markdown: https://insights.sbomify.com/CVE-2021-47396/index.md)","id":"CVE-2021-47396","markdown":"https://insights.sbomify.com/CVE-2021-47396/index.md","name":"CVE-2021-47396","record":{"aliases":["DEBIAN-CVE-2021-47396","GHSA-cwq4-fr9x-6844","UBUNTU-CVE-2021-47396"],"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 flaw in the Linux kernel mac80211-hwsim module causes system stalls when beacon timers fire late, requiring a patch to prevent denial of service.","user_interaction":"not_required","vuln_class":"denial_of_service"},"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":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmac80211-hwsim: fix late beacon hrtimer handling\n\nThomas explained in https://lore.kernel.org/r/87mtoeb4hb.ffs@tglx\nthat our handling of the hrtimer here is wrong: If the timer fires\nlate (e.g. due to vCPU scheduling, as reported by Dmitry/syzbot)\nthen it tries to actually rearm the timer at the next deadline,\nwhich might be in the past already:\n\n 1          2          3          N          N+1\n |          |          |   ...    |          |\n\n ^ intended to fire here (1)\n            ^ next deadline here (2)\n                                      ^ actually fired here\n\nThe next time it fires, it's later, but will still try to schedule\nfor the next deadline (now 3), etc. until it catches up with N,\nbut that might take a long time, causing stalls etc.\n\nNow, all of this is simulation, so we just have to fix it, but\nnote that the behaviour is wrong even per spec, since there's no\nvalue then in sending all those beacons unaligned - they should be\naligned to the TBTT (1, 2, 3, ... in the picture), and if we're a\nbit (or a lot) late, then just resume at that point.\n\nTherefore, change the code to use hrtimer_forward_now() which will\nensure that the next firing of the timer would be at N+1 (in the\npicture), i.e. the next interval point after the current time.","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":"mac80211-hwsim: fix late beacon hrtimer handling","id":"CVE-2021-47396","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"denial_of_service","year":"2021"},"n_packages":0,"n_references":4,"next":{"headline":"sctp: break out if skb_header_pointer returns NULL in sctp_rcv_ootb","id":"CVE-2021-47397"},"packages":[],"prev":{"headline":"mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap","id":"CVE-2021-47395"},"products":["Linux"],"published":"2024-05-21","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":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-05-11","vendors":["Linux"]},"summary":"A flaw in the Linux kernel mac80211-hwsim module causes system stalls when beacon timers fire late, requiring a patch to prevent denial of service.","url":"https://insights.sbomify.com/CVE-2021-47396/"}