CVE-2025-40271

What is known

In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix uaf in proc_readdir_de() Pde is erased from subdir rbtree through rb_erase(), but not set the node to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE() set the erased node to EMPTY, then pde_subdir_next() will return NULL to avoid uaf access. We found an uaf issue while using stress-ng testing, need to run testcase getdent and tun in the same time. The steps of the issue is as follows: 1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current pde is tun3; 2) in the [time windows] unregister netdevice tun3 and tun2, and erase them from rbtree. erase tun3 first, and then erase tun2. the pde(tun2) will be released to slab; 3) continue to getdent process, then pde_subdir_next() will return pde(tun2) which is released, it will case uaf access. CPU 0 | CPU 1 ------------------------------------------------------------------------- traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2 sys_getdents64() | iterate_dir() | proc_readdir() | proc_readdir_de() | snmp6_unregister_dev() pde_get(de); | proc_remove() read_unlock(&proc_subdir_lock); | remove_proc_subtree() | write_lock(&proc_subdir_lock); [time window] | rb_erase(&root->subdir_node, &parent->subdir); | write_unlock(&proc_subdir_lock); read_lock(&proc_subdir_lock); | next = pde_subdir_next(de); | pde_put(de); | de = next; //UAF | rbtree of dev_snmp6 | pde(tun3) / \ NULL pde(tun2)

Business impact

Successful exploitation of CVE-2025-40271, a high vulnerability (CVSS 7.8) affecting the affected product, may affect the confidentiality, integrity or availability of the vulnerable environment. The exact impact depends on the installed version, exposed interfaces and deployment configuration.

Recommended administrator action

Confirm whether the affected product is present and compare installed versions with the vendor advisory and NVD record. Apply the vendor patch or documented mitigation; until remediation is complete, reduce exposure of affected interfaces, review relevant logs and monitor for indicators of exploitation. DataHouse can support version verification, managed patching, network exposure reduction, log review and backup validation for dedicated, cloud and colocated environments.

Sources

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