{"id":"CVE-2026-31478","state":"PUBLISHED","title":"ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()\n\nAfter this commit (e2b76ab8b5c9 \"ksmbd: add support for read compound\"),\nresponse buffer management was changed to use dynamic iov array.\nIn the new design, smb2_calc_max_out_buf_len() expects the second\nargument (hdr2_len) to be the offset of ->Buffer field in the\nresponse structure, not a hardcoded magic number.\nFix the remaining call sites to use the correct offsetof() value.","publishedAt":"2026-04-22T13:54:06.157Z","updatedAt":"2026-10-19T18:45:53.152Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/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":"f2283680a80571ca82d710bc6ecd8f8beac67d63","status":"affected","lessThan":"70b4c414889492c522b6e4331562360f49be2361","versionType":"git"},{"version":"9f297df20d93411c0b4ddad7f88ba04a7cd36e77","status":"affected","lessThan":"9a7166f0ef8cbb7bb48dd05e2471d995566003f5","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"6aef1765d6807e0f027cd87f6ac973eb0879a46d","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"80824c7e527b70cf9039534e60aff592e8f209d1","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"4cb537ae4f37d7d0f617815ed4bed7173fb50861","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"0e55f63dd08f09651d39e1b709a91705a8a0ddcb","versionType":"git"},{"version":"5.15.145","status":"affected","lessThan":"5.15.203","versionType":"semver"},{"version":"6.1.71","status":"affected","lessThan":"6.1.168","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smb2pdu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"5.15.203","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.168","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.131","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.80","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.21","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.11","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","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/smb2pdu.c"]}],"references":["https://git.kernel.org/stable/c/70b4c414889492c522b6e4331562360f49be2361","https://git.kernel.org/stable/c/9a7166f0ef8cbb7bb48dd05e2471d995566003f5","https://git.kernel.org/stable/c/c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683","https://git.kernel.org/stable/c/6aef1765d6807e0f027cd87f6ac973eb0879a46d","https://git.kernel.org/stable/c/80824c7e527b70cf9039534e60aff592e8f209d1","https://git.kernel.org/stable/c/4cb537ae4f37d7d0f617815ed4bed7173fb50861","https://git.kernel.org/stable/c/0e55f63dd08f09651d39e1b709a91705a8a0ddcb"],"weaknesses":["CWE-131"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31478.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31478","state":"PUBLISHED","datePublished":"2026-04-22T13:54:06.157Z","dateUpdated":"2026-10-19T18:45:53.152Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.098Z"},"containers":{"cna":{"title":"ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()\n\nAfter this commit (e2b76ab8b5c9 \"ksmbd: add support for read compound\"),\nresponse buffer management was changed to use dynamic iov array.\nIn the new design, smb2_calc_max_out_buf_len() expects the second\nargument (hdr2_len) to be the offset of ->Buffer field in the\nresponse structure, not a hardcoded magic number.\nFix the remaining call sites to use the correct offsetof() value."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f2283680a80571ca82d710bc6ecd8f8beac67d63","status":"affected","lessThan":"70b4c414889492c522b6e4331562360f49be2361","versionType":"git"},{"version":"9f297df20d93411c0b4ddad7f88ba04a7cd36e77","status":"affected","lessThan":"9a7166f0ef8cbb7bb48dd05e2471d995566003f5","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"6aef1765d6807e0f027cd87f6ac973eb0879a46d","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"80824c7e527b70cf9039534e60aff592e8f209d1","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"4cb537ae4f37d7d0f617815ed4bed7173fb50861","versionType":"git"},{"version":"e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d","status":"affected","lessThan":"0e55f63dd08f09651d39e1b709a91705a8a0ddcb","versionType":"git"},{"version":"5.15.145","status":"affected","lessThan":"5.15.203","versionType":"semver"},{"version":"6.1.71","status":"affected","lessThan":"6.1.168","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smb2pdu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"5.15.203","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.168","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.131","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.80","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.21","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.11","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","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/smb2pdu.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/70b4c414889492c522b6e4331562360f49be2361"},{"url":"https://git.kernel.org/stable/c/9a7166f0ef8cbb7bb48dd05e2471d995566003f5"},{"url":"https://git.kernel.org/stable/c/c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683"},{"url":"https://git.kernel.org/stable/c/6aef1765d6807e0f027cd87f6ac973eb0879a46d"},{"url":"https://git.kernel.org/stable/c/80824c7e527b70cf9039534e60aff592e8f209d1"},{"url":"https://git.kernel.org/stable/c/4cb537ae4f37d7d0f617815ed4bed7173fb50861"},{"url":"https://git.kernel.org/stable/c/0e55f63dd08f09651d39e1b709a91705a8a0ddcb"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable code is in ksmbd SMB2 request handling reachable over TCP SMB connections, including normal network-facing port 445 deployments.\nAC:L - An attacker controls the SMB2 compound request layout, output buffer lengths, and command sequence needed to reach the miscalculation; no race or external timing condition is required.\nPR:N - The handlers run after SMB session/tree setup, but ksmbd supports guest/anonymous sessions and guest shares, so a reasonable deployment allows a remote attacker to reach the path without credentials.\nUI:N - No victim action is required after the ksmbd service is exposed; the attacker sends crafted SMB2 requests directly.\nS:U - The impact remains within the kernel/ksmbd security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The bug can cause out-of-bounds kernel response-buffer memory corruption in compound SMB2 handling, which is defensibly treatable as exploitable memory corruption with potential information disclosure.\nI:H - The incorrect length calculation can permit an out-of-bounds write past the ksmbd response buffer, and kernel OOB writes are scored as high integrity impact.\nA:H - Even if not weaponized for code execution, the out-of-bounds kernel write can crash or oops the kernel, causing high availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:22:57.123Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.145","versionEndExcluding":"5.15.203"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.71","versionEndExcluding":"6.1.168"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.6.131"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.12.80"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.18.21"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.19.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-31478","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:09:58.409155Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-131","lang":"en","type":"CWE","description":"CWE-131 Incorrect Calculation of Buffer Size"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:45:53.152Z"}}]}}}