CVE-2025-21731

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

  1. 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)

  1. step 1) release the reference;

  2. 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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < e70a578487a47d7cf058904141e586684d1c3381affected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < 6bef6222a3f6c7adb6396f77f25a3579d821b09aaffected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < e3be8862d73cac833e0fb7602636c19c6cb94b11affected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < e7343fa33751cb07c1c56b666bf37cfca357130eaffected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < d208d2c52b652913b5eefc8ca434b0d6b757f68faffected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739affected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302affected
LinuxLinuxb7aa3d39385dc2d95899f9e379623fef446a2acd < 844b8cdc681612ff24df62cdefddeab5772fadf1affected
LinuxLinux4.12affected
LinuxLinux0 < 4.12unaffected
LinuxLinux5.4.291 <= 5.4.*unaffected
LinuxLinux5.10.235 <= 5.10.*unaffected
LinuxLinux5.15.179 <= 5.15.*unaffected
LinuxLinux6.1.129 <= 6.1.*unaffected
LinuxLinux6.6.76 <= 6.6.*unaffected
LinuxLinux6.12.13 <= 6.12.*unaffected
LinuxLinux6.13.2 <= 6.13.*unaffected
LinuxLinux6.14 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

CVE Program Container

Additional References

References