smb: client: validate dacloffset before building DACL pointers

Summary

In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building DACL pointers parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor. On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths. Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points.

Timeline

1. May 28, 2026, 9:36 AM UTCCVE published
2. Oct 16, 2026, 3:20 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

3. Oct 19, 2026, 7:36 PM UTCRecord last updated

Affected versions

• Linux Linux

  From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in 5de2665e913a10ad70aaeecf736b97276e83d995; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in f9dc3be8f403c1216df73e57221f44b045e7ee0b; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in ba7f71b6161c0943dafc367565e5843d16b7d505; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in 3b1ddba19e77ee35241cd27f16dc3e8d14e08db7; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in c688f3ed73d31943334ad2139cb02ec49664322a; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in 8bd07e417b6bda67e317920584e48cb6ee442a8a; From bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 · fixed in f98b48151cc502ada59d9778f0112d21f2586ca3

• Linux Linux

  5.12

• KernelLinux

  From 5.12.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.140; From 6.7.0 · fixed in 6.12.88; From 6.13.0 · fixed in 6.18.30; From 6.19.0 · fixed in 7.0.7

References 7