{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53390","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-06-09T07:44:35.402Z","datePublished":"2026-07-19T12:01:54.951Z","dateUpdated":"2026-08-17T04:50:41.549Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:50:41.549Z"},"descriptions":[{"lang":"en","value":"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()."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"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()."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"],"versions":[{"version":"282cbbb476b9f35793452bc461934af4c7eca169","lessThan":"c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0","status":"affected","versionType":"git"},{"version":"f20adc4ef7428bc485ee83fd1a592252fb87718b","lessThan":"988c93d3bba066d8669143e6ec30bb2be9608d53","status":"affected","versionType":"git"},{"version":"325d4ac11f526cb8964cff14548ccf02d8c756d8","lessThan":"36599894fa8536fefdf1e296c0af71b8b7226859","status":"affected","versionType":"git"},{"version":"95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c","lessThan":"d5c81a095c86fe507c032d08f3a8cfc518444927","status":"affected","versionType":"git"},{"version":"90089584b2e25c4510b7b987387b4405f0673ece","lessThan":"7627ff8c4f9919f14de562b0160ab4ec9d80b1f7","status":"affected","versionType":"git"},{"version":"d07b26f39246a82399661936dd0c853983cfade7","lessThan":"e36e35660adb9b8ef1435ac359151dda5f094c55","status":"affected","versionType":"git"},{"version":"d07b26f39246a82399661936dd0c853983cfade7","lessThan":"1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b","status":"affected","versionType":"git"},{"version":"151b1799861fde38087c08f613abc2843ef597b0","status":"affected","versionType":"git"},{"version":"5.15.210","lessThan":"5.15.212","status":"affected","versionType":"semver"},{"version":"6.1.176","lessThan":"6.1.177","status":"affected","versionType":"semver"},{"version":"6.6.140","lessThan":"6.6.144","status":"affected","versionType":"semver"},{"version":"6.12.84","lessThan":"6.12.95","status":"affected","versionType":"semver"},{"version":"6.18.25","lessThan":"6.18.38","status":"affected","versionType":"semver"},{"version":"7.0.2","lessThan":"7.1","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"],"versions":[{"version":"7.1","status":"affected"},{"version":"0","lessThan":"7.1","status":"unaffected","versionType":"semver"},{"version":"5.15.212","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.177","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.144","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.95","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.38","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.3","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.210","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.176","versionEndExcluding":"6.1.177"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.140","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.84","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.25","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.1","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.1","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0"},{"url":"https://git.kernel.org/stable/c/988c93d3bba066d8669143e6ec30bb2be9608d53"},{"url":"https://git.kernel.org/stable/c/36599894fa8536fefdf1e296c0af71b8b7226859"},{"url":"https://git.kernel.org/stable/c/d5c81a095c86fe507c032d08f3a8cfc518444927"},{"url":"https://git.kernel.org/stable/c/7627ff8c4f9919f14de562b0160ab4ec9d80b1f7"},{"url":"https://git.kernel.org/stable/c/e36e35660adb9b8ef1435ac359151dda5f094c55"},{"url":"https://git.kernel.org/stable/c/1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b"}],"title":"ksmbd: fix out-of-bounds read in smb_check_perm_dacl()","x_generator":{"engine":"bippy-1.2.0"}}}}