{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2021-46936", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-46936", "idYear": 2021, "status": "PUBLISHED", "publishedAt": "2024-02-27T09:44:02.758Z", "updatedAt": "2026-08-05T08:45:10.624Z", "importedAt": "2026-10-24T01:56:36.661Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "net: fix use-after-free in tw_timer_handler", "summary": "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 \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": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "15579e1301f856ad9385d720c9267c11032a5022" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "e73164e89d1be561228a4534e1091369ee4ba41a" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "5c2fe20ad37ff56070ae0acb34152333976929b4" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "a8e1944b44f94f5c5f530e434c5eaee787254566" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "fe5838c22b986c1190f1dce9aa09bf6a491c1a69" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "2386e81a1d277f540e1285565c9d41d531bb69d4" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "08eacbd141e2495d2fcdde84358a06c4f95cbb13" }, { "version": "61a7e26028b94805fd686a6dc9dbd9941f8f19b0", "status": "affected", "versionType": "git", "lessThan": "e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "2.6.27", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "2.6.27" }, { "version": "4.4.298", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "4.4.*" }, { "version": "4.9.296", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "4.9.*" }, { "version": "4.14.261", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "4.14.*" }, { "version": "4.19.224", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "4.19.*" }, { "version": "5.4.170", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.4.*" }, { "version": "5.10.90", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.13", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "5.16", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }