{"id":"AZL-85386","summary":"CVE-2026-31709 affecting package kernel for versions less than 6.6.141.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: validate the whole DACL before rewriting it in cifsacl\n\nbuild_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a\nserver-supplied dacloffset and then use the incoming ACL to rebuild the\nchmod/chown security descriptor.\n\nThe original fix only checked that the struct smb_acl header fits before\nreading dacl_ptr-\u003esize or dacl_ptr-\u003enum_aces.  That avoids the immediate\nheader-field OOB read, but the rewrite helpers still walk ACEs based on\npdacl-\u003enum_aces with no structural validation of the incoming DACL body.\n\nA malicious server can return a truncated DACL that still contains a\nheader, claims one or more ACEs, and then drive\nreplace_sids_and_copy_aces() or set_chmod_dacl() past the validated\nextent while they compare or copy attacker-controlled ACEs.\n\nFactor the DACL structural checks into validate_dacl(), extend them to\nvalidate each ACE against the DACL bounds, and use the shared validator\nbefore the chmod/chown rebuild paths.  parse_dacl() reuses the same\nvalidator so the read-side parser and write-side rewrite paths agree on\nwhat constitutes a well-formed incoming DACL.","modified":"2026-08-29T05:27:27Z","published":"2026-05-01T14:16:20Z","upstream":["CVE-2026-31709"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31709"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.141.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-85386.json"}}],"schema_version":"1.9.0"}