{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-46936","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-02-25T13:45:52.720Z","datePublished":"2024-02-27T09:44:02.758Z","dateUpdated":"2025-05-04T07:00:40.694Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2025-05-04T07:00:40.694Z"},"descriptions":[{"lang":"en","value":"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     <IRQ>\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->mib.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"}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/af_inet.c"],"versions":[{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"15579e1301f856ad9385d720c9267c11032a5022","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"e73164e89d1be561228a4534e1091369ee4ba41a","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"5c2fe20ad37ff56070ae0acb34152333976929b4","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"a8e1944b44f94f5c5f530e434c5eaee787254566","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"fe5838c22b986c1190f1dce9aa09bf6a491c1a69","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"2386e81a1d277f540e1285565c9d41d531bb69d4","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"08eacbd141e2495d2fcdde84358a06c4f95cbb13","status":"affected","versionType":"git"},{"version":"61a7e26028b94805fd686a6dc9dbd9941f8f19b0","lessThan":"e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/af_inet.c"],"versions":[{"version":"2.6.27","status":"affected"},{"version":"0","lessThan":"2.6.27","status":"unaffected","versionType":"semver"},{"version":"4.4.298","lessThanOrEqual":"4.4.*","status":"unaffected","versionType":"semver"},{"version":"4.9.296","lessThanOrEqual":"4.9.*","status":"unaffected","versionType":"semver"},{"version":"4.14.261","lessThanOrEqual":"4.14.*","status":"unaffected","versionType":"semver"},{"version":"4.19.224","lessThanOrEqual":"4.19.*","status":"unaffected","versionType":"semver"},{"version":"5.4.170","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.90","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.13","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"5.16","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"4.4.298"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"4.9.296"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"4.14.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"4.19.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"5.4.170"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"5.10.90"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"5.15.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.27","versionEndExcluding":"5.16"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/15579e1301f856ad9385d720c9267c11032a5022"},{"url":"https://git.kernel.org/stable/c/e73164e89d1be561228a4534e1091369ee4ba41a"},{"url":"https://git.kernel.org/stable/c/5c2fe20ad37ff56070ae0acb34152333976929b4"},{"url":"https://git.kernel.org/stable/c/a8e1944b44f94f5c5f530e434c5eaee787254566"},{"url":"https://git.kernel.org/stable/c/fe5838c22b986c1190f1dce9aa09bf6a491c1a69"},{"url":"https://git.kernel.org/stable/c/2386e81a1d277f540e1285565c9d41d531bb69d4"},{"url":"https://git.kernel.org/stable/c/08eacbd141e2495d2fcdde84358a06c4f95cbb13"},{"url":"https://git.kernel.org/stable/c/e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0"}],"title":"net: 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