CVE Catalog

CVE-2026-97559

Unknown
Published: Translated: NVD NIST

Summary

In the Linux kernel's SMB client, a problem was found in DACL rewrite: the size accumulator using u16 can wrap, leading to corruption of the DACL sent to the server. The fix changes the type to u32 and returns -EOVERFLOW on overflow.

Risk Assessment

DACL corruption can lead to incorrect file permissions or errors on SMB shared resources.

Recommendation

Apply the Linux kernel patch that uses u32 for size calculation and returns -EOVERFLOW on overflow.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: smb: client: fail DACL rewrite when the new DACL exceeds 64K replace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of the DACL they build in a u16. That accumulator can wrap. validate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) / 20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can grow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with one carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is therefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond what a u16 can hold. A wraparound is reached with 863 ACEs. After the wraparound, ndacl_ptr->size becomes meaningless and the offset will point anywhere in the ACE array. As a result, we will see corruption of the DACL, which then gets sent to the server. This is not an out-of-bounds write as the allocation now covers the worst-case expansion, so writes will always go into the buffer. Adjust the code to use a u32 internally and return -EOVERFLOW in the overflow case. The operation must be refused, because a DACL can only hold 2^16-1 bytes on the wire and larger DACLs cannot be represented. set_chmod_dacl() carries the same pattern and is fixed the same way. It only wraps once the source DACL comes within roughly 380 bytes of the 64K ceiling, but the failure mode is identical.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS