{"api_version":"1","generated_at":"2026-10-01T04:01:52+00:00","cve":"CVE-2026-97559","urls":{"html":"https://cve.report/CVE-2026-97559","api":"https://cve.report/api/cve/CVE-2026-97559.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-97559","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-97559"},"summary":{"title":"smb: client: fail DACL rewrite when the new DACL exceeds 64K","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16. That accumulator can wrap.\n\nvalidate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) /\n20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can\ngrow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with\none carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is\ntherefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond\nwhat a u16 can hold. A wraparound is reached with 863 ACEs.\n\nAfter the wraparound, ndacl_ptr->size becomes meaningless and the offset\nwill point anywhere in the ACE array. As a result, we will see\ncorruption of the DACL, which then gets sent to the server. This is not\nan out-of-bounds write as the allocation now covers the worst-case\nexpansion, so writes will always go into the buffer.\n\nAdjust the code to use a u32 internally and return -EOVERFLOW in the\noverflow case. The operation must be refused, because a DACL can only\nhold 2^16-1 bytes on the wire and larger DACLs cannot be represented.\n\nset_chmod_dacl() carries the same pattern and is fixed the same way. It\nonly wraps once the source DACL comes within roughly 380 bytes of the\n64K ceiling, but the failure mode is identical.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-25 11:17:06","updated_at":"2026-09-25 11:17:06"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/2ef532a01f44687f5b95001e88247cf05bff9892","name":"https://git.kernel.org/stable/c/2ef532a01f44687f5b95001e88247cf05bff9892","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ee13d687d06a6fbb2008625dd560c654231b28e0","name":"https://git.kernel.org/stable/c/ee13d687d06a6fbb2008625dd560c654231b28e0","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d05045177a855386bca5e1909e08d06290e6e3b3","name":"https://git.kernel.org/stable/c/d05045177a855386bca5e1909e08d06290e6e3b3","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97559","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97559","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f5065508897a922327f32223082325d10b069ebc 2ef532a01f44687f5b95001e88247cf05bff9892 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f5065508897a922327f32223082325d10b069ebc ee13d687d06a6fbb2008625dd560c654231b28e0 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f5065508897a922327f32223082325d10b069ebc d05045177a855386bca5e1909e08d06290e6e3b3 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.12","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.12 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.53 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.7 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"97559","cve":"CVE-2026-97559","epss":"0.001980000","percentile":"0.085910000","score_date":"2026-09-27","updated_at":"2026-09-28 00:02:24"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/client/cifsacl.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"2ef532a01f44687f5b95001e88247cf05bff9892","status":"affected","version":"f5065508897a922327f32223082325d10b069ebc","versionType":"git"},{"lessThan":"ee13d687d06a6fbb2008625dd560c654231b28e0","status":"affected","version":"f5065508897a922327f32223082325d10b069ebc","versionType":"git"},{"lessThan":"d05045177a855386bca5e1909e08d06290e6e3b3","status":"affected","version":"f5065508897a922327f32223082325d10b069ebc","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/smb/client/cifsacl.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.12"},{"lessThan":"5.12","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.53","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.7","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.53","versionStartIncluding":"5.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.7","versionStartIncluding":"5.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc3","versionStartIncluding":"5.12","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16. That accumulator can wrap.\n\nvalidate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) /\n20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can\ngrow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with\none carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is\ntherefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond\nwhat a u16 can hold. A wraparound is reached with 863 ACEs.\n\nAfter the wraparound, ndacl_ptr->size becomes meaningless and the offset\nwill point anywhere in the ACE array. As a result, we will see\ncorruption of the DACL, which then gets sent to the server. This is not\nan out-of-bounds write as the allocation now covers the worst-case\nexpansion, so writes will always go into the buffer.\n\nAdjust the code to use a u32 internally and return -EOVERFLOW in the\noverflow case. The operation must be refused, because a DACL can only\nhold 2^16-1 bytes on the wire and larger DACLs cannot be represented.\n\nset_chmod_dacl() carries the same pattern and is fixed the same way. It\nonly wraps once the source DACL comes within roughly 380 bytes of the\n64K ceiling, but the failure mode is identical."}],"providerMetadata":{"dateUpdated":"2026-09-25T10:21:48.866Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/2ef532a01f44687f5b95001e88247cf05bff9892"},{"url":"https://git.kernel.org/stable/c/ee13d687d06a6fbb2008625dd560c654231b28e0"},{"url":"https://git.kernel.org/stable/c/d05045177a855386bca5e1909e08d06290e6e3b3"}],"title":"smb: client: fail DACL rewrite when the new DACL exceeds 64K","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-97559","datePublished":"2026-09-25T10:21:48.866Z","dateReserved":"2026-09-24T16:01:01.155Z","dateUpdated":"2026-09-25T10:21:48.866Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-25 11:17:06","lastModifiedDate":"2026-09-25 11:17:06","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"97559","Ordinal":"1","Title":"smb: client: fail DACL rewrite when the new DACL exceeds 64K","CVE":"CVE-2026-97559","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"97559","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16. That accumulator can wrap.\n\nvalidate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) /\n20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can\ngrow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with\none carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is\ntherefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond\nwhat a u16 can hold. A wraparound is reached with 863 ACEs.\n\nAfter the wraparound, ndacl_ptr->size becomes meaningless and the offset\nwill point anywhere in the ACE array. As a result, we will see\ncorruption of the DACL, which then gets sent to the server. This is not\nan out-of-bounds write as the allocation now covers the worst-case\nexpansion, so writes will always go into the buffer.\n\nAdjust the code to use a u32 internally and return -EOVERFLOW in the\noverflow case. The operation must be refused, because a DACL can only\nhold 2^16-1 bytes on the wire and larger DACLs cannot be represented.\n\nset_chmod_dacl() carries the same pattern and is fixed the same way. It\nonly wraps once the source DACL comes within roughly 380 bytes of the\n64K ceiling, but the failure mode is identical.","Type":"Description","Title":"smb: client: fail DACL rewrite when the new DACL exceeds 64K"}]}}}