{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-53390", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-53390" ], "published": "2026-07-19T12:02:32Z", "summary": "ksmbd: fix out-of-bounds read in smb_check_perm_dacl()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix out-of-bounds read in smb_check_perm_dacl()\n\nThe permission-check ACE walk in smb_check_perm_dacl() validates the ACE\nheader size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it\nnever checks that ace->size is actually large enough to contain\nnum_subauth sub-authorities before compare_sids() dereferences them.\n\nCIFS_SID_BASE_SIZE covers the SID header up to but excluding the\nsub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header,\nso the existing guards only guarantee the 8-byte SID base, i.e. zero\nsub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for\ni < min(local_sid->num_subauth, ace->sid.num_subauth). The local\ncomparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid()\nresult) always have at least one sub-authority, and an attacker controls\nthe ACE revision and authority bytes (which lie within the in-bounds SID\nbase), so they can match one of those SIDs and force the sub_auth read.\n\nA crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of\nthe security descriptor therefore causes a heap out-of-bounds read of up\nto SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd\nallocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr()\ninto a buffer sized exactly to the on-disk data (kzalloc(sd_size) in\nndr_decode_v4_ntacl()), so the read lands past the allocation. The\nmalformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL\nis not normalised before being written to the security.NTACL xattr) and\nthe read fires on a subsequent SMB2_CREATE access check, making this\nreachable by an authenticated client on a share that uses ACL xattrs.\n\nAdd the missing num_subauth-versus-ace_size check, mirroring the\nidentical guards already present in the sibling parsers parse_dacl() and\nsmb_inherit_dacl().", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.87-1+rpt1~bookworm", "1:6.12.93-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.87+rpt-rpi-2712", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v6", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v7l", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.87+rpt-rpi-v8-rt", "binary_version": "1:6.12.87-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-2712", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v6", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v7", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v7l", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v8", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v8-rt", "binary_version": "1:6.12.93-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.12.87-1+rpt1~bookworm": { "linux_commit": "ae4d75fb36deba0fe1a986d9bfae65755e082dd0", "upstream_version": "6.12.87", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.95" }, "1:6.12.93-1+rpt1": { "linux_commit": "d8ab4e908235da7727f22dd36ad5af224671677d", "upstream_version": "6.12.93", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.95" } } } }, { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v6", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v7", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.38" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.38" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.38" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-53390" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/988c93d3bba066d8669143e6ec30bb2be9608d53" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/36599894fa8536fefdf1e296c0af71b8b7226859" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d5c81a095c86fe507c032d08f3a8cfc518444927" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7627ff8c4f9919f14de562b0160ab4ec9d80b1f7" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e36e35660adb9b8ef1435ac359151dda5f094c55" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-17T05:24:08Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 8.1, "cvss_v3_severity": "High", "scenario": "AV:N - The bug is reachable through ksmbd's in-kernel SMB2 server on TCP/445 via SMB2_SET_INFO (to store a crafted security descriptor) and SMB2_CREATE (to trigger the DACL walk), with packets handled from ksmbd_conn_handler_loop() through smb2_set_info()/smb2_open() into smb_check_perm_dacl().\nAC:L - An attacker fully controls the malformed ACE fields (size, num_subauth, revision, authority bytes) and can reliably place the ACE at the tail of a security descriptor, store it verbatim, then trigger the read on the next CREATE without depending on race timing or uncontrollable memory layout.\nPR:L - Exploitation requires a completed SMB2 session and share access: SMB2_SET_INFO needs FILE_WRITE_DAC/FILE_WRITE_OWNER on an open file, and the poisoned descriptor is only persisted on shares with ACL xattr support, which is authenticated low-privilege client access rather than pre-auth or host root.\nUI:N - No end-user action is required beyond the attacker sending crafted SMB2 protocol messages over the network; no victim must open a file, mount a share, or perform any interactive step.\nS:U - The vulnerability is confined to kernel heap memory reads during ksmbd DACL permission evaluation and does not cross a security boundary such as guest-to-host VM escape or sandbox escape.\nC:H - compare_sids() performs a heap out-of-bounds read of up to SID_MAX_SUB_AUTHORITIES (15) sub-authority dwords (60 bytes) past the kzalloc()-sized security descriptor buffer, exposing adjacent kernel heap contents even though the data is not returned in the SMB response.\nI:N - The flaw is a read-only out-of-bounds access in compare_sids() with no memory write, type confusion, or demonstrated control-flow hijack primitive; integrity is not directly compromised.\nA:H - Reading past the end of the kmalloc allocation can fault the kernel (oops/panic), and a malicious descriptor planted on a shared file can deny availability to any other authenticated client whose SMB2_CREATE triggers smb_check_perm_dacl()." } } }