{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-46936 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-46936 is a high-severity use after free vulnerability in Linux kernel, published on 27 Feb 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-2021-46936 and fix it if it is affected.\n\nWhat it is: CVE-2021-46936 is a high-severity use after free vulnerability in Linux kernel, published on 27 Feb 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-2021-46936 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-2021-46936/ (Markdown: https://insights.sbomify.com/CVE-2021-46936/index.md)","id":"CVE-2021-46936","markdown":"https://insights.sbomify.com/CVE-2021-46936/index.md","name":"CVE-2021-46936","record":{"aliases":["DEBIAN-CVE-2021-46936","GHSA-9x4x-qwhq-g8f7","UBUNTU-CVE-2021-46936"],"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 use-after-free in the Linux kernel's network timer handler can cause a system panic, leading to denial of service.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"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":[{"id":"CWE-416","name":"Use After Free"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix use-after-free in tw_timer_handler\n\nA real world panic issue was found as follow in Linux 5.4.\n\n    BUG: unable to handle page fault for address: ffffde49a863de28\n    PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0\n    RIP: 0010:tw_timer_handler+0x20/0x40\n    Call Trace:\n     \u003cIRQ\u003e\n     call_timer_fn+0x2b/0x120\n     run_timer_softirq+0x1ef/0x450\n     __do_softirq+0x10d/0x2b8\n     irq_exit+0xc7/0xd0\n     smp_apic_timer_interrupt+0x68/0x120\n     apic_timer_interrupt+0xf/0x20\n\nThis issue was also reported since 2017 in the thread [1],\nunfortunately, the issue was still can be reproduced after fixing\nDCCP.\n\nThe ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net\nnamespace is destroyed since tcp_sk_ops is registered befrore\nipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops\nin the list of pernet_list. There will be a use-after-free on\nnet-\u003emib.net_statistics in tw_timer_handler after ipv4_mib_exit_net\nif there are some inflight time-wait timers.\n\nThis bug is not introduced by commit f2bf415cfed7 (\"mib: add net to\nNET_ADD_STATS_BH\") since the net_statistics is a global variable\ninstead of dynamic allocation and freeing. Actually, commit\n61a7e26028b9 (\"mib: put net statistics on struct net\") introduces\nthe bug since it put net statistics on struct net and free it when\nnet namespace is destroyed.\n\nMoving init_ipv4_mibs() to the front of tcp_init() to fix this bug\nand replace pr_crit() with panic() since continuing is meaningless\nwhen init_ipv4_mibs() fails.\n\n[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1","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":"net: fix use-after-free in tw_timer_handler","id":"CVE-2021-46936","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"use_after_free","year":"2021"},"n_packages":0,"n_references":8,"next":{"headline":"mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()'","id":"CVE-2021-46937"},"packages":[],"prev":{"headline":"binder: fix async_free_space accounting for empty parcels","id":"CVE-2021-46935"},"products":["Linux"],"published":"2024-02-27","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":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-08-05","vendors":["Linux"]},"summary":"A use-after-free in the Linux kernel's network timer handler can cause a system panic, leading to denial of service.","url":"https://insights.sbomify.com/CVE-2021-46936/"}