{"id":"CVE-2026-43050","title":"atm: lec: fix use-after-free in sock_def_readable()","summary":"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 s…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3e8b25f32f2f35549d03d77da030a24a45bdef5b","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 750a33f417f3d196b86375f8d9f8938bacf130fe","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 317843d5355062020649124eb4a0d7acbcc3f53e","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b256d055da47258e63f8b40965f276c5f23d229a","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3989740fa4978e1d2d51ecc62be1b01093e104ad","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < abc10f85a3965ac14b9ed7ad3e67b35604a63aa3","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 5fbbb1ff936d7ff9528d929c1549977e8123d8a8","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 922814879542c2e397b0e9641fd36b8202a8e555","Linux 2.6.12"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T15:27:14.542294Z"},"published":"2026-05-01","updated":"2026-11-06","sourceUpdated":"2026-11-06T15:32:28.420Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-43050","references":[{"url":"https://git.kernel.org/stable/c/3e8b25f32f2f35549d03d77da030a24a45bdef5b"},{"url":"https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe"},{"url":"https://git.kernel.org/stable/c/317843d5355062020649124eb4a0d7acbcc3f53e"},{"url":"https://git.kernel.org/stable/c/b256d055da47258e63f8b40965f276c5f23d229a"},{"url":"https://git.kernel.org/stable/c/3989740fa4978e1d2d51ecc62be1b01093e104ad"},{"url":"https://git.kernel.org/stable/c/abc10f85a3965ac14b9ed7ad3e67b35604a63aa3"},{"url":"https://git.kernel.org/stable/c/5fbbb1ff936d7ff9528d929c1549977e8123d8a8"},{"url":"https://git.kernel.org/stable/c/922814879542c2e397b0e9641fd36b8202a8e555"}],"tags":["cve.org"],"epss":0.00119,"epssPercentile":0.01754,"ingestedAt":"2026-11-06T15:54:04.030Z","slug":"CVE-2026-43050","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3e8b25f32f2f35549d03d77da030a24a45bdef5b`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 750a33f417f3d196b86375f8d9f8938bacf130fe`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 317843d5355062020649124eb4a0d7acbcc3f53e`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b256d055da47258e63f8b40965f276c5f23d229a`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3989740fa4978e1d2d51ecc62be1b01093e104ad`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < abc10f85a3965ac14b9ed7ad3e67b35604a63aa3`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 5fbbb1ff936d7ff9528d929c1549977e8123d8a8`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 922814879542c2e397b0e9641fd36b8202a8e555`\n- `Linux 2.6.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}