{"api_version":"1","generated_at":"2026-05-03T12:43:01+00:00","cve":"CVE-2026-31712","urls":{"html":"https://cve.report/CVE-2026-31712","api":"https://cve.report/api/cve/CVE-2026-31712.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31712","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31712"},"summary":{"title":"ksmbd: require minimum ACE size in smb_check_perm_dacl()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require minimum ACE size in smb_check_perm_dacl()\n\nBoth ACE-walk loops in smb_check_perm_dacl() only guard against an\nunder-sized remaining buffer, not against an ACE whose declared\n`ace->size` is smaller than the struct it claims to describe:\n\n  if (offsetof(struct smb_ace, access_req) > aces_size)\n      break;\n  ace_size = le16_to_cpu(ace->size);\n  if (ace_size > aces_size)\n      break;\n\nThe first check only requires the 4-byte ACE header to be in bounds;\nit does not require access_req (4 bytes at offset 4) to be readable.\nAn attacker who has set a crafted DACL on a file they own can declare\nace->size == 4 with aces_size == 4, pass both checks, and then\n\n  granted |= le32_to_cpu(ace->access_req);               /* upper loop */\n  compare_sids(&sid, &ace->sid);                         /* lower loop */\n\nreads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at\noffset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES\n* 4 bytes).\n\nTighten both loops to require\n\n  ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE\n\nwhich is the smallest valid on-wire ACE layout (4-byte header +\n4-byte access_req + 8-byte sid base with zero sub-auths).  Also\nreject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES\nbefore letting compare_sids() dereference sub_auth[] entries.\n\nparse_sec_desc() already enforces an equivalent check (lines 441-448);\nsmb_check_perm_dacl() simply grew weaker validation over time.\n\nReachability: authenticated SMB client with permission to set an ACL\non a file.  On a subsequent CREATE against that file, the kernel\nwalks the stored DACL via smb_check_perm_dacl() and triggers the\nOOB read.  Not pre-auth, and the OOB read is not reflected to the\nattacker, but KASAN reports and kernel state corruption are\npossible.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-05-01 14:16:21","updated_at":"2026-05-03 07:16:18"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.3","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","baseScore":8.3,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"LOW","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.3","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","data":{"baseScore":8.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/151b1799861fde38087c08f613abc2843ef597b0","name":"https://git.kernel.org/stable/c/151b1799861fde38087c08f613abc2843ef597b0","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d07b26f39246a82399661936dd0c853983cfade7","name":"https://git.kernel.org/stable/c/d07b26f39246a82399661936dd0c853983cfade7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c","name":"https://git.kernel.org/stable/c/95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/90089584b2e25c4510b7b987387b4405f0673ece","name":"https://git.kernel.org/stable/c/90089584b2e25c4510b7b987387b4405f0673ece","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31712","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31712","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 90089584b2e25c4510b7b987387b4405f0673ece git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 151b1799861fde38087c08f613abc2843ef597b0 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 d07b26f39246a82399661936dd0c853983cfade7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.15","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.84 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.25 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.2 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"31712","cve":"CVE-2026-31712","epss":"0.000180000","percentile":"0.046600000","score_date":"2026-05-02","updated_at":"2026-05-03 00:00:23"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/server/smbacl.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c","status":"affected","version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","versionType":"git"},{"lessThan":"90089584b2e25c4510b7b987387b4405f0673ece","status":"affected","version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","versionType":"git"},{"lessThan":"151b1799861fde38087c08f613abc2843ef597b0","status":"affected","version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","versionType":"git"},{"lessThan":"d07b26f39246a82399661936dd0c853983cfade7","status":"affected","version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/smb/server/smbacl.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.15"},{"lessThan":"5.15","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.84","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.25","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.2","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.84","versionStartIncluding":"5.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.25","versionStartIncluding":"5.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.2","versionStartIncluding":"5.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1-rc1","versionStartIncluding":"5.15","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require minimum ACE size in smb_check_perm_dacl()\n\nBoth ACE-walk loops in smb_check_perm_dacl() only guard against an\nunder-sized remaining buffer, not against an ACE whose declared\n`ace->size` is smaller than the struct it claims to describe:\n\n  if (offsetof(struct smb_ace, access_req) > aces_size)\n      break;\n  ace_size = le16_to_cpu(ace->size);\n  if (ace_size > aces_size)\n      break;\n\nThe first check only requires the 4-byte ACE header to be in bounds;\nit does not require access_req (4 bytes at offset 4) to be readable.\nAn attacker who has set a crafted DACL on a file they own can declare\nace->size == 4 with aces_size == 4, pass both checks, and then\n\n  granted |= le32_to_cpu(ace->access_req);               /* upper loop */\n  compare_sids(&sid, &ace->sid);                         /* lower loop */\n\nreads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at\noffset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES\n* 4 bytes).\n\nTighten both loops to require\n\n  ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE\n\nwhich is the smallest valid on-wire ACE layout (4-byte header +\n4-byte access_req + 8-byte sid base with zero sub-auths).  Also\nreject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES\nbefore letting compare_sids() dereference sub_auth[] entries.\n\nparse_sec_desc() already enforces an equivalent check (lines 441-448);\nsmb_check_perm_dacl() simply grew weaker validation over time.\n\nReachability: authenticated SMB client with permission to set an ACL\non a file.  On a subsequent CREATE against that file, the kernel\nwalks the stored DACL via smb_check_perm_dacl() and triggers the\nOOB read.  Not pre-auth, and the OOB read is not reflected to the\nattacker, but KASAN reports and kernel state corruption are\npossible."}],"metrics":[{"cvssV3_1":{"baseScore":8.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-05-03T05:45:35.398Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c"},{"url":"https://git.kernel.org/stable/c/90089584b2e25c4510b7b987387b4405f0673ece"},{"url":"https://git.kernel.org/stable/c/151b1799861fde38087c08f613abc2843ef597b0"},{"url":"https://git.kernel.org/stable/c/d07b26f39246a82399661936dd0c853983cfade7"}],"title":"ksmbd: require minimum ACE size in smb_check_perm_dacl()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-31712","datePublished":"2026-05-01T13:56:08.583Z","dateReserved":"2026-03-09T15:48:24.133Z","dateUpdated":"2026-05-03T05:45:35.398Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-05-01 14:16:21","lastModifiedDate":"2026-05-03 07:16:18","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","baseScore":8.3,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"LOW","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.5}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31712","Ordinal":"1","Title":"ksmbd: require minimum ACE size in smb_check_perm_dacl()","CVE":"CVE-2026-31712","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31712","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require minimum ACE size in smb_check_perm_dacl()\n\nBoth ACE-walk loops in smb_check_perm_dacl() only guard against an\nunder-sized remaining buffer, not against an ACE whose declared\n`ace->size` is smaller than the struct it claims to describe:\n\n  if (offsetof(struct smb_ace, access_req) > aces_size)\n      break;\n  ace_size = le16_to_cpu(ace->size);\n  if (ace_size > aces_size)\n      break;\n\nThe first check only requires the 4-byte ACE header to be in bounds;\nit does not require access_req (4 bytes at offset 4) to be readable.\nAn attacker who has set a crafted DACL on a file they own can declare\nace->size == 4 with aces_size == 4, pass both checks, and then\n\n  granted |= le32_to_cpu(ace->access_req);               /* upper loop */\n  compare_sids(&sid, &ace->sid);                         /* lower loop */\n\nreads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at\noffset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES\n* 4 bytes).\n\nTighten both loops to require\n\n  ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE\n\nwhich is the smallest valid on-wire ACE layout (4-byte header +\n4-byte access_req + 8-byte sid base with zero sub-auths).  Also\nreject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES\nbefore letting compare_sids() dereference sub_auth[] entries.\n\nparse_sec_desc() already enforces an equivalent check (lines 441-448);\nsmb_check_perm_dacl() simply grew weaker validation over time.\n\nReachability: authenticated SMB client with permission to set an ACL\non a file.  On a subsequent CREATE against that file, the kernel\nwalks the stored DACL via smb_check_perm_dacl() and triggers the\nOOB read.  Not pre-auth, and the OOB read is not reflected to the\nattacker, but KASAN reports and kernel state corruption are\npossible.","Type":"Description","Title":"ksmbd: require minimum ACE size in smb_check_perm_dacl()"}]}}}