{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64400","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T15:36:31.785Z","datePublished":"2026-07-25T08:50:43.655Z","dateUpdated":"2026-08-17T04:54:57.921Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:54:57.921Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: prevent path traversal bypass by restricting caseless retry\n\nksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path\nresolution within the share root. When a crafted path attempts to\nescape the share boundary using parent-directory components ('..'),\nvfs_path_parent_lookup() detects this and immediately fails,\nreturning -EXDEV.\n\nHowever, a bug exists in __ksmbd_vfs_kern_path() under caseless mode.\nThe function fails to intercept the -EXDEV error and erroneously\nfalls through to the caseless retry logic, which is intended only\nfor genuinely missing files. During this retry process, the path\nis reconstructed, leading to an unintended LOOKUP_BENEATH bypass\nthat allows write-capable users to create zero-length files or\ndirectories outside the exported share.\n\nFix this by ensuring that the execution only proceeds to the caseless\nlookup retry when the error is specifically -ENOENT. Any other errors,\nsuch as -EXDEV from a path traversal attempt, must be returned immediately."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","baseScore":8.6,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable lookup is reached remotely through SMB2 CREATE requests handled by ksmbd over TCP/445.\nAC:L - The attacker controls the crafted parent-directory path and can issue repeated or concurrent requests; any required lookup/create race is attacker-driven.\nPR:N - Although a valid SMB session and writable tree connection are required, ksmbd supports anonymous guest sessions on writable shares, requiring no prior privileges in a reasonable deployment.\nUI:N - Exploitation requires only attacker-generated SMB requests and no action by a victim.\nS:U - The bypass affects filesystems managed by the same host kernel and does not cross a virtualization or comparable security authority boundary.\nC:L - File contents are not exposed, but the out-of-share caseless directory walk and distinguishable errors can disclose limited pathname-existence metadata.\nI:L - The attacker can create chosen zero-length files or directories outside the export, but cannot supply file contents or overwrite arbitrary existing data through this flaw.\nA:H - Repeated creation in an escaped world-writable location can exhaust root-filesystem inodes, storage, or tmpfs memory and cause system-wide service unavailability."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/vfs.c"],"versions":[{"version":"74d7970febf7e9005375aeda0df821d2edffc9f7","lessThan":"8c9a4f1327eb71efbf14842e7b8a6d965077eb67","status":"affected","versionType":"git"},{"version":"74d7970febf7e9005375aeda0df821d2edffc9f7","lessThan":"54bab9ba5a9f156ffa9324fcbe5a356fd0242f95","status":"affected","versionType":"git"},{"version":"019aae488dbc67c97a33db03652e20e2c9e3afa7","status":"affected","versionType":"git"},{"version":"6927ffe7479c72e7ebf885507227266a75f7c97d","status":"affected","versionType":"git"},{"version":"ef6cc1c465786b3e4e735d1ab8b616b3e94402df","status":"affected","versionType":"git"},{"version":"5.15.145","lessThan":"5.16","status":"affected","versionType":"semver"},{"version":"6.1.71","lessThan":"6.2","status":"affected","versionType":"semver"},{"version":"6.3.10","lessThan":"6.4","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/vfs.c"],"versions":[{"version":"6.4","status":"affected"},{"version":"0","lessThan":"6.4","status":"unaffected","versionType":"semver"},{"version":"7.1.4","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":"6.4","versionEndExcluding":"7.1.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.71"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3.10"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67"},{"url":"https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95"}],"title":"ksmbd: prevent path traversal bypass by restricting caseless retry","x_generator":{"engine":"bippy-1.2.0"}}}}