CVE-2025-21731High· 7.8▾ TwilightIn 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(…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 42.9 · likelihood 0 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Jul 14.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.2%
0.2% → 0.2%
In the Linux kernel, the following vulnerability has been resolved:
nbd: don't allow reconnect after disconnect
Following process can cause nbd_config UAF:
grab nbd_config temporarily;
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
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)
step 1) release the reference;
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.
linux_kernel >= 4.12, < 5.4.291linux_kernel >= 5.5, < 5.10.235linux_kernel >= 5.11, < 5.15.179linux_kernel >= 5.16, < 6.1.129linux_kernel >= 6.2, < 6.6.76linux_kernel >= 6.7, < 6.12.13linux_kernel >= 6.13, < 6.13.2Upgrade past the affected range:
linux_kernel 6.13.2Connected by shared product, vendor, weakness, or advisory.
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