CVE-2025-68803

In the Linux kernel, the following vulnerability has been resolved:

NFSD: NFSv4 file creation neglects setting ACL

An NFSv4 client that sets an ACL with a named principal during file creation retrieves the ACL afterwards, and finds that it is only a default ACL (based on the mode bits) and not the ACL that was requested during file creation. This violates RFC 8881 section 6.4.1.3: the ACL attribute is set as given.

The issue occurs in nfsd_create_setattr(), which calls nfsd_attrs_valid() to determine whether to call nfsd_setattr(). However, nfsd_attrs_valid() checks only for iattr changes and security labels, but not POSIX ACLs. When only an ACL is present, the function returns false, nfsd_setattr() is skipped, and the POSIX ACL is never applied to the inode.

Subsequently, when the client retrieves the ACL, the server finds no POSIX ACL on the inode and returns one generated from the files mode bits rather than returning the originally-specified ACL.

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Affected Software

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References

• https://git.kernel.org/stable/c/214b396480061cbc8b16f2c518b2add7fbfa5192
• https://git.kernel.org/stable/c/381261f24f4e4b41521c0e5ef5cc0b9a786a9862
• https://git.kernel.org/stable/c/60dbdef2ebc2317266a385e4debdb1bb0e57afe1
• https://git.kernel.org/stable/c/75f91534f9acdfef77f8fa094313b7806f801725
• https://git.kernel.org/stable/c/913f7cf77bf14c13cfea70e89bcb6d0b22239562
• https://git.kernel.org/stable/c/bf4e671c651534a307ab2fabba4926116beef8c3
• https://git.kernel.org/stable/c/c182e1e0b7640f6bcc0c5ca8d473f7c57199ea3d
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html