{"id":"CVE-2026-64257","state":"PUBLISHED","title":"smb: client: reject overlapping data areas in SMB2 responses","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject overlapping data areas in SMB2 responses\n\nCommit 53b7c271f06b (\"smb: client: restrict implied bcc[0] exemption to\nresponses without data area\") restricted the implied bcc[0] length\nexception to responses without a data area. However, the overlap\nhandling in __smb2_calc_size() clears data_length, which can make an\ninvalid response appear to have no data area and so qualify for the\nexception.\n\nTrack data area overlap separately and reject such responses before\napplying the length compatibility exceptions.","publishedAt":"2026-07-25T08:49:09.345Z","updatedAt":"2026-08-17T04:52:09.787Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"31c6312608c60b72a1feb99a5afb680645a3e8a3","status":"affected","lessThan":"445ece263131780dee273d727a4d6f11934feec7","versionType":"git"},{"version":"573e502d14714d2947e22e7eff40ec20a6a44a42","status":"affected","lessThan":"36bfa52459e45c0d5b668de2f1c91f6dc5c67775","versionType":"git"},{"version":"419ec1b604d7fb60c10aec2dc062371f9fcd4940","status":"affected","lessThan":"4a9d2657d3e05f6ed09c148cb127b4e58702275f","versionType":"git"},{"version":"ceb875a375dedbf51c9425c1d13a2d7a8435c08c","status":"affected","lessThan":"fdafa1e68dc75045b7b617e6e7d2854950804d83","versionType":"git"},{"version":"6e9d10f62773b99bd927940fd9cbdfe7207e23ff","status":"affected","lessThan":"57cba95f0e97c6f6e45e6731da30aff091bd7460","versionType":"git"},{"version":"53b7c271f06be4dd5cfc8c6ef552a8355c891a7f","status":"affected","lessThan":"8986c932905ea508d66da421eb2eb6e676ace1fe","versionType":"git"},{"version":"8d0bbc78046d264bbf6a574ea6f9072258a43e35","status":"affected","versionType":"git"},{"version":"b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0","status":"affected","versionType":"git"},{"version":"5.10.261","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.15.212","status":"affected","lessThan":"5.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2misc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2misc.c"]}],"references":["https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7","https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775","https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f","https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83","https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460","https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64257.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64257","state":"PUBLISHED","datePublished":"2026-07-25T08:49:09.345Z","dateUpdated":"2026-08-17T04:52:09.787Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.773Z"},"containers":{"cna":{"title":"smb: client: reject overlapping data areas in SMB2 responses","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject overlapping data areas in SMB2 responses\n\nCommit 53b7c271f06b (\"smb: client: restrict implied bcc[0] exemption to\nresponses without data area\") restricted the implied bcc[0] length\nexception to responses without a data area. However, the overlap\nhandling in __smb2_calc_size() clears data_length, which can make an\ninvalid response appear to have no data area and so qualify for the\nexception.\n\nTrack data area overlap separately and reject such responses before\napplying the length compatibility exceptions."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"31c6312608c60b72a1feb99a5afb680645a3e8a3","status":"affected","lessThan":"445ece263131780dee273d727a4d6f11934feec7","versionType":"git"},{"version":"573e502d14714d2947e22e7eff40ec20a6a44a42","status":"affected","lessThan":"36bfa52459e45c0d5b668de2f1c91f6dc5c67775","versionType":"git"},{"version":"419ec1b604d7fb60c10aec2dc062371f9fcd4940","status":"affected","lessThan":"4a9d2657d3e05f6ed09c148cb127b4e58702275f","versionType":"git"},{"version":"ceb875a375dedbf51c9425c1d13a2d7a8435c08c","status":"affected","lessThan":"fdafa1e68dc75045b7b617e6e7d2854950804d83","versionType":"git"},{"version":"6e9d10f62773b99bd927940fd9cbdfe7207e23ff","status":"affected","lessThan":"57cba95f0e97c6f6e45e6731da30aff091bd7460","versionType":"git"},{"version":"53b7c271f06be4dd5cfc8c6ef552a8355c891a7f","status":"affected","lessThan":"8986c932905ea508d66da421eb2eb6e676ace1fe","versionType":"git"},{"version":"8d0bbc78046d264bbf6a574ea6f9072258a43e35","status":"affected","versionType":"git"},{"version":"b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0","status":"affected","versionType":"git"},{"version":"5.10.261","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.15.212","status":"affected","lessThan":"5.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2misc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/smb2misc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7"},{"url":"https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775"},{"url":"https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f"},{"url":"https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83"},{"url":"https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460"},{"url":"https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","baseScore":9.1,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - A malicious or compromised SMB server can deliver the crafted SMB2 response over TCP during client negotiation.\nAC:L - The overlapping offset and oversized length are attacker-controlled and deterministically bypass validation; no race or uncontrolled memory layout is required to trigger the out-of-bounds read.\nPR:N - The vulnerable NEGOTIATE response is processed before SMB authentication or signature verification, requiring no privileges or credentials on the target.\nUI:N - An already configured SMB mount can negotiate during automatic mounting or reconnection without a human opening crafted content.\nS:U - The vulnerable parser and the affected kernel memory remain within the Linux kernel's security authority.\nC:H - The validation mismatch permits an attacker-controlled ASN.1 length to read far beyond the 448-byte receive object, potentially traversing tens of kilobytes of adjacent kernel memory.\nI:N - The investigated paths provide an out-of-bounds read but no out-of-bounds write, use-after-free, type confusion, or other arbitrary modification primitive.\nA:H - The slab out-of-bounds access is repeatable and can produce a kernel fault or panic, particularly on hardened or memory-safety-instrumented deployments."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:52:09.787Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.212"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}