{"id":"CVE-2026-72382","state":"PUBLISHED","title":"ksmbd: reject undersized DACLs before parsing ACEs","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: reject undersized DACLs before parsing ACEs\n\nparse_dacl() limits the attacker-controlled ACE count by comparing it\nwith the number of minimal ACEs that fit in the DACL size. The DACL size\nfield is 16 bits, but the expression subtracts sizeof(struct smb_acl).\nBecause sizeof() is unsigned, a DACL size smaller than the ACL header\nunderflows to a large size_t.\n\nA malicious client can reach this with:\n\nSMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY)\n  -> smb2_set_info_sec()\n  -> set_info_sec()\n  -> parse_sec_desc()\n  -> parse_dacl()\n     -> init_acl_state(..., 0xffff)\n     -> init_acl_state(..., 0xffff)\n     -> kmalloc_objs(..., 0xffff)\n\nThus a malformed security descriptor can make num_aces pass the guard\nand drive large temporary ACL state and pointer-array allocations.\n\nReject DACLs smaller than struct smb_acl before doing the subtraction,\nso the ACE count check cannot be bypassed by the underflow.","publishedAt":"2026-08-15T05:56:14.103Z","updatedAt":"2026-10-30T12:29:13.532Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"8dc949061e35427433feac3ebe5ec089f2aa857e","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"16fb65ec15fe7c90f50a2115854bfd9a032d4023","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"282847c0cf22f2e961155ac8e42f6eeab7e16049","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"d020e7f27bf65eecd3805404702f716b2b6d9e73","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"60908f7ebcd9b6cde74ad5711fab0f49c7970949","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"]}],"references":["https://git.kernel.org/stable/c/8dc949061e35427433feac3ebe5ec089f2aa857e","https://git.kernel.org/stable/c/16fb65ec15fe7c90f50a2115854bfd9a032d4023","https://git.kernel.org/stable/c/282847c0cf22f2e961155ac8e42f6eeab7e16049","https://git.kernel.org/stable/c/d020e7f27bf65eecd3805404702f716b2b6d9e73","https://git.kernel.org/stable/c/15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd","https://git.kernel.org/stable/c/60908f7ebcd9b6cde74ad5711fab0f49c7970949"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72382.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72382","state":"PUBLISHED","datePublished":"2026-08-15T05:56:14.103Z","dateUpdated":"2026-10-30T12:29:13.532Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.923Z"},"containers":{"cna":{"title":"ksmbd: reject undersized DACLs before parsing ACEs","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: reject undersized DACLs before parsing ACEs\n\nparse_dacl() limits the attacker-controlled ACE count by comparing it\nwith the number of minimal ACEs that fit in the DACL size. The DACL size\nfield is 16 bits, but the expression subtracts sizeof(struct smb_acl).\nBecause sizeof() is unsigned, a DACL size smaller than the ACL header\nunderflows to a large size_t.\n\nA malicious client can reach this with:\n\nSMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY)\n  -> smb2_set_info_sec()\n  -> set_info_sec()\n  -> parse_sec_desc()\n  -> parse_dacl()\n     -> init_acl_state(..., 0xffff)\n     -> init_acl_state(..., 0xffff)\n     -> kmalloc_objs(..., 0xffff)\n\nThus a malformed security descriptor can make num_aces pass the guard\nand drive large temporary ACL state and pointer-array allocations.\n\nReject DACLs smaller than struct smb_acl before doing the subtraction,\nso the ACE count check cannot be bypassed by the underflow."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"8dc949061e35427433feac3ebe5ec089f2aa857e","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"16fb65ec15fe7c90f50a2115854bfd9a032d4023","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"282847c0cf22f2e961155ac8e42f6eeab7e16049","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"d020e7f27bf65eecd3805404702f716b2b6d9e73","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"60908f7ebcd9b6cde74ad5711fab0f49c7970949","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/8dc949061e35427433feac3ebe5ec089f2aa857e"},{"url":"https://git.kernel.org/stable/c/16fb65ec15fe7c90f50a2115854bfd9a032d4023"},{"url":"https://git.kernel.org/stable/c/282847c0cf22f2e961155ac8e42f6eeab7e16049"},{"url":"https://git.kernel.org/stable/c/d020e7f27bf65eecd3805404702f716b2b6d9e73"},{"url":"https://git.kernel.org/stable/c/15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd"},{"url":"https://git.kernel.org/stable/c/60908f7ebcd9b6cde74ad5711fab0f49c7970949"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The flaw is reached through ksmbd's in-kernel SMB2 server on TCP/445 via SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY) or SMB2 CREATE with an SD buffer, both handled from remote network input.\nAC:L - An attacker reliably triggers the bug by sending a crafted security descriptor with DACL size below 8 bytes and a large num_aces (e.g. 0xFFFF), bypassing the underflowed ACE-count check without special timing or victim state.\nPR:L - Exploitation requires an authenticated SMB session, a writable tree connect, an open file handle (or CREATE with SD buffer), and FILE_WRITE_DAC or FILE_WRITE_OWNER access on that object.\nUI:N - No victim interaction is required beyond the attacker sending malicious SMB2 protocol requests to an exposed ksmbd server.\nS:U - Impact is confined to kernel memory exhaustion and ksmbd availability within the same host security authority; it does not cross VM, container, or IOMMU boundaries.\nC:H - The unsigned underflow bypasses DACL bounds validation, letting attacker-controlled num_aces drive multi-megabyte kernel heap allocations and parse attacker-supplied ACE data from malformed security descriptors.\nI:H - Attacker-controlled allocation sizing from bypassed validation creates large heap manipulation primitives in kernel context, consistent with similar ksmbd DACL integer-validation flaws scored at high integrity impact.\nA:H - Each malicious request forces roughly 2.5 MB of kernel allocations; repeated or concurrent SMB2_SET_INFO calls can exhaust memory, trigger OOM/page-allocator failures, and deny service to ksmbd and the host."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:29:13.532Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}