{"cve":"CVE-2026-43050","nvd":{"published":"2026-05-01T15:16:51.403","modified":"2026-06-17T10:48:50.253","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\natm: lec: fix use-after-free in sock_def_readable()\n\nA race condition exists between lec_atm_close() setting priv->lecd\nto NULL and concurrent access to priv->lecd in send_to_lecd(),\nlec_handle_bridge(), and lec_atm_send(). When the socket is freed\nvia RCU while another thread is still using it, a use-after-free\noccurs in sock_def_readable() when accessing the socket's wait queue.\n\nThe root cause is that lec_atm_close() clears priv->lecd without\nany synchronization, while callers dereference priv->lecd without\nany protection against concurrent teardown.\n\nFix this by converting priv->lecd to an RCU-protected pointer:\n- Mark priv->lecd as __rcu in lec.h\n- Use rcu_assign_pointer() in lec_atm_close() and lecd_attach()\n  for safe pointer assignment\n- Use rcu_access_pointer() for NULL checks that do not dereference\n  the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and\n  lecd_attach()\n- Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(),\n  lec_handle_bridge() and lec_atm_send() to safely access lecd\n- Use rcu_assign_pointer() followed by synchronize_rcu() in\n  lec_atm_close() to ensure all readers have completed before\n  proceeding. This is safe since lec_atm_close() is called from\n  vcc_release() which holds lock_sock(), a sleeping lock.\n- Remove the manual sk_receive_queue drain from lec_atm_close()\n  since vcc_destroy_socket() already drains it after lec_atm_close()\n  returns.\n\nv2: Switch from spinlock + sock_hold/put approach to RCU to properly\n    fix the race. The v1 spinlock approach had two issues pointed out\n    by Eric Dumazet:\n    1. priv->lecd was still accessed directly after releasing the\n       lock instead of using a local copy.\n    2. The spinlock did not prevent packets being queued after\n       lec_atm_close() drains sk_receive_queue since timer and\n       workqueue paths bypass netif_stop_queue().\n\nNote: Syzbot patch testing was attempted but the test VM terminated\n    unexpectedly with \"Connection to localhost closed by remote host\",\n    likely due to a QEMU AHCI emulation issue unrelated to this fix.\n    Compile testing with \"make W=1 net/atm/lec.o\" passes cleanly.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.0},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/317843d5355062020649124eb4a0d7acbcc3f53e","https://git.kernel.org/stable/c/3989740fa4978e1d2d51ecc62be1b01093e104ad","https://git.kernel.org/stable/c/3e8b25f32f2f35549d03d77da030a24a45bdef5b","https://git.kernel.org/stable/c/5fbbb1ff936d7ff9528d929c1549977e8123d8a8","https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:33:09.003606135+00:00"},"epss":{"cve":"CVE-2026-43050","score":0.00119,"percentile":0.01731,"date":"2026-11-01"},"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."]}