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CVE-2025-21731

nbd: don't allow reconnect after disconnect

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in e70a578487a47d7cf058904141e586684d1c3381; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in 6bef6222a3f6c7adb6396f77f25a3579d821b09a; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in e3be8862d73cac833e0fb7602636c19c6cb94b11; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in e7343fa33751cb07c1c56b666bf37cfca357130e; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in d208d2c52b652913b5eefc8ca434b0d6b757f68f; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302; From b7aa3d39385dc2d95899f9e379623fef446a2acd · fixed in 844b8cdc681612ff24df62cdefddeab5772fadf1

  • Linux Linux

    4.12

  • KernelLinux

    From 4.12.0 · fixed in 5.4.291; From 5.5.0 · fixed in 5.10.235; From 5.11.0 · fixed in 5.15.179; From 5.16.0 · fixed in 6.1.129; From 6.2.0 · fixed in 6.6.76; From 6.7.0 · fixed in 6.12.13; From 6.13.0 · fixed in 6.13.2

References 8

git.kernel.org