CVE-2026-43050 (GCVE-0-2026-43050)

Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-02 06:14
VLAI?
Title
atm: lec: fix use-after-free in sock_def_readable()
Summary
In the Linux kernel, the following vulnerability has been resolved: atm: lec: fix use-after-free in sock_def_readable() A race condition exists between lec_atm_close() setting priv->lecd to NULL and concurrent access to priv->lecd in send_to_lecd(), lec_handle_bridge(), and lec_atm_send(). When the socket is freed via RCU while another thread is still using it, a use-after-free occurs in sock_def_readable() when accessing the socket's wait queue. The root cause is that lec_atm_close() clears priv->lecd without any synchronization, while callers dereference priv->lecd without any protection against concurrent teardown. Fix this by converting priv->lecd to an RCU-protected pointer: - Mark priv->lecd as __rcu in lec.h - Use rcu_assign_pointer() in lec_atm_close() and lecd_attach() for safe pointer assignment - Use rcu_access_pointer() for NULL checks that do not dereference the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and lecd_attach() - Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(), lec_handle_bridge() and lec_atm_send() to safely access lecd - Use rcu_assign_pointer() followed by synchronize_rcu() in lec_atm_close() to ensure all readers have completed before proceeding. This is safe since lec_atm_close() is called from vcc_release() which holds lock_sock(), a sleeping lock. - Remove the manual sk_receive_queue drain from lec_atm_close() since vcc_destroy_socket() already drains it after lec_atm_close() returns. v2: Switch from spinlock + sock_hold/put approach to RCU to properly fix the race. The v1 spinlock approach had two issues pointed out by Eric Dumazet: 1. priv->lecd was still accessed directly after releasing the lock instead of using a local copy. 2. The spinlock did not prevent packets being queued after lec_atm_close() drains sk_receive_queue since timer and workqueue paths bypass netif_stop_queue(). Note: Syzbot patch testing was attempted but the test VM terminated unexpectedly with "Connection to localhost closed by remote host", likely due to a QEMU AHCI emulation issue unrelated to this fix. Compile testing with "make W=1 net/atm/lec.o" passes cleanly.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 3e8b25f32f2f35549d03d77da030a24a45bdef5b (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 750a33f417f3d196b86375f8d9f8938bacf130fe (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 317843d5355062020649124eb4a0d7acbcc3f53e (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < b256d055da47258e63f8b40965f276c5f23d229a (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 3989740fa4978e1d2d51ecc62be1b01093e104ad (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < abc10f85a3965ac14b9ed7ad3e67b35604a63aa3 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5fbbb1ff936d7ff9528d929c1549977e8123d8a8 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 922814879542c2e397b0e9641fd36b8202a8e555 (git)
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    Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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          "lang": "en",
          "value": "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-\u003elecd\nto NULL and concurrent access to priv-\u003elecd 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\u0027s wait queue.\n\nThe root cause is that lec_atm_close() clears priv-\u003elecd without\nany synchronization, while callers dereference priv-\u003elecd without\nany protection against concurrent teardown.\n\nFix this by converting priv-\u003elecd to an RCU-protected pointer:\n- Mark priv-\u003elecd 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-\u003elecd 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."
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          "url": "https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe"
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          "url": "https://git.kernel.org/stable/c/922814879542c2e397b0e9641fd36b8202a8e555"
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      "title": "atm: lec: fix use-after-free in sock_def_readable()",
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    "cveId": "CVE-2026-43050",
    "datePublished": "2026-05-01T14:15:44.542Z",
    "dateReserved": "2026-05-01T14:12:55.979Z",
    "dateUpdated": "2026-05-02T06:14:36.377Z",
    "state": "PUBLISHED"
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      "cve": "CVE-2026-43050",
      "date": "2026-05-04",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43050\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-01T15:16:51.403\",\"lastModified\":\"2026-05-01T15:24:14.893\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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-\u003elecd\\nto NULL and concurrent access to priv-\u003elecd 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\u0027s wait queue.\\n\\nThe root cause is that lec_atm_close() clears priv-\u003elecd without\\nany synchronization, while callers dereference priv-\u003elecd without\\nany protection against concurrent teardown.\\n\\nFix this by converting priv-\u003elecd to an RCU-protected pointer:\\n- Mark priv-\u003elecd 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-\u003elecd 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.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/317843d5355062020649124eb4a0d7acbcc3f53e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3989740fa4978e1d2d51ecc62be1b01093e104ad\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3e8b25f32f2f35549d03d77da030a24a45bdef5b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5fbbb1ff936d7ff9528d929c1549977e8123d8a8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/922814879542c2e397b0e9641fd36b8202a8e555\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/abc10f85a3965ac14b9ed7ad3e67b35604a63aa3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b256d055da47258e63f8b40965f276c5f23d229a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.