{"id":"AZL-104523","summary":"CVE-2026-97555 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix heap overflow in DACL owner/group rewrite\n\nWhen id_mode_to_cifs_acl rewrites an existing DACL, it allocates a\nbuffer sized according to the on-disk DACL length reported by\ndacl_ptr-\u003esize. However, replace_sids_and_copy_aces may rewrite each\nACE with a new owner/group SID obtained from the cifs.idmap upcall.\nThose SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,\nmaking each ACE up to 76 bytes (sizeof(struct smb_ace)).\n\nIf the original DACL contains short SIDs (e.g., 1 sub-authority) while\nthe replacement SIDs are long, the rewritten ACEs overflow the\nallocation.\n\nFix this by always budgeting for worst-case SID expansion: allocate\nsizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which\ncovers the smb_acl header and room for every ACE at maximum SID size.\nThis replaces the previous split logic that used dacl_ptr-\u003esize for\ncifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid\nmounts: both paths can trigger the same rewrite and need the same\nheadroom.\n\nKASAN reports this as:\n  BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]\n  Write of size 4 at addr ffff8881a5e25374 by task chown/5298\n  ...\n  The buggy address is located 0 bytes to the right of\n   allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)","modified":"2026-09-27T05:34:32Z","published":"2026-09-25T11:17:05Z","upstream":["CVE-2026-97555"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97555"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-104523.json"}}],"schema_version":"1.9.0"}