CVE-2025-21796

Summary

CVE-2025-21796 is a vulnerability affecting the Linux kernel's nfsd component. The issue lies in the handling of Posix Access Control Lists (ACLs). Specifically, when the kernel fails to obtain acl_default, both acl_access and acl_default are released simultaneously. However, acl_access still retains a pointer to the released posix_acl, leading to a use-after-free condition. This can trigger a WARNING message and potentially result in a kernel panic. To mitigate this issue, developers are advised to ensure that acl_access/acl_default are properly released after use.

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