{"cve":"CVE-2024-44991","nvd":{"published":"2024-09-04T20:15:08.150","modified":"2026-06-17T07:53:22.463","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: prevent concurrent execution of tcp_sk_exit_batch\n\nIts possible that two threads call tcp_sk_exit_batch() concurrently,\nonce from the cleanup_net workqueue, once from a task that failed to clone\na new netns.  In the latter case, error unwinding calls the exit handlers\nin reverse order for the 'failed' netns.\n\ntcp_sk_exit_batch() calls tcp_twsk_purge().\nProblem is that since commit b099ce2602d8 (\"net: Batch inet_twsk_purge\"),\nthis function picks up twsk in any dying netns, not just the one passed\nin via exit_batch list.\n\nThis means that the error unwind of setup_net() can \"steal\" and destroy\ntimewait sockets belonging to the exiting netns.\n\nThis allows the netns exit worker to proceed to call\n\nWARN_ON_ONCE(!refcount_dec_and_test(&net->ipv4.tcp_death_row.tw_refcount));\n\nwithout the expected 1 -> 0 transition, which then splats.\n\nAt same time, error unwind path that is also running inet_twsk_purge()\nwill splat as well:\n\nWARNING: .. at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210\n...\n refcount_dec include/linux/refcount.h:351 [inline]\n inet_twsk_kill+0x758/0x9c0 net/ipv4/inet_timewait_sock.c:70\n inet_twsk_deschedule_put net/ipv4/inet_timewait_sock.c:221\n inet_twsk_purge+0x725/0x890 net/ipv4/inet_timewait_sock.c:304\n tcp_sk_exit_batch+0x1c/0x170 net/ipv4/tcp_ipv4.c:3522\n ops_exit_list+0x128/0x180 net/core/net_namespace.c:178\n setup_net+0x714/0xb40 net/core/net_namespace.c:375\n copy_net_ns+0x2f0/0x670 net/core/net_namespace.c:508\n create_new_namespaces+0x3ea/0xb10 kernel/nsproxy.c:110\n\n... because refcount_dec() of tw_refcount unexpectedly dropped to 0.\n\nThis doesn't seem like an actual bug (no tw sockets got lost and I don't\nsee a use-after-free) but as erroneous trigger of debug check.\n\nAdd a mutex to force strict ordering: the task that calls tcp_twsk_purge()\nblocks other task from doing final _dec_and_test before mutex-owner has\nremoved all tw sockets of dying netns.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/565d121b69980637f040eb4d84289869cdaabedf","https://git.kernel.org/stable/c/99580ae890ec8bd98b21a2a9c6668f8f1555b62e","https://git.kernel.org/stable/c/e3d9de3742f4d5c47ae35f888d3023a5b54fcd2f","https://git.kernel.org/stable/c/f6fd2dbf584a4047ba88d1369ff91c9851261ec1","https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:54:16.205165117+00:00"},"epss":{"cve":"CVE-2024-44991","score":0.00245,"percentile":0.15806,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}