{"id":"CVE-2026-43185","state":"PUBLISHED","title":"ksmbd: fix signededness bug in smb_direct_prepare_negotiation()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix signededness bug in smb_direct_prepare_negotiation()\n\nsmb_direct_prepare_negotiation() casts an unsigned __u32 value\nfrom sp->max_recv_size and req->preferred_send_size to a signed\nint before computing min_t(int, ...). A maliciously provided\npreferred_send_size of 0x80000000 will return as smaller than\nmax_recv_size, and then be used to set the maximum allowed\nalowed receive size for the next message.\n\nBy sending a second message with a large value (>1420 bytes)\nthe attacker can then achieve a heap buffer overflow.\n\nThis fix replaces min_t(int, ...) with min_t(u32)","publishedAt":"2026-05-06T11:27:56.386Z","updatedAt":"2026-10-30T12:25:08.090Z","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":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"56eab82fa6fb5ca024b0514e249d40d9b23ee5a7","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"a110dbe928561d440e9e117d17331139a0bedace","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"ceae058eb707ddd0d68f0872f9d9f23b7c30c37b","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"55abc475d096da4a5356b6efb0cfdc6156bc1550","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"6b4f875aac344cdd52a1f34cc70ed2f874a65757","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/transport_rdma.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","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/transport_rdma.c"]}],"references":["https://git.kernel.org/stable/c/1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c","https://git.kernel.org/stable/c/56eab82fa6fb5ca024b0514e249d40d9b23ee5a7","https://git.kernel.org/stable/c/a110dbe928561d440e9e117d17331139a0bedace","https://git.kernel.org/stable/c/ceae058eb707ddd0d68f0872f9d9f23b7c30c37b","https://git.kernel.org/stable/c/55abc475d096da4a5356b6efb0cfdc6156bc1550","https://git.kernel.org/stable/c/6b4f875aac344cdd52a1f34cc70ed2f874a65757"],"weaknesses":[],"ingestedAt":"2026-10-30T12:42:04.495Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43185.json","commit":"db8103c5921aac81d5d90efcf3745980dafabf49","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43185","state":"PUBLISHED","datePublished":"2026-05-06T11:27:56.386Z","dateUpdated":"2026-10-30T12:25:08.090Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:55.991Z"},"containers":{"cna":{"title":"ksmbd: fix signededness bug in smb_direct_prepare_negotiation()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix signededness bug in smb_direct_prepare_negotiation()\n\nsmb_direct_prepare_negotiation() casts an unsigned __u32 value\nfrom sp->max_recv_size and req->preferred_send_size to a signed\nint before computing min_t(int, ...). A maliciously provided\npreferred_send_size of 0x80000000 will return as smaller than\nmax_recv_size, and then be used to set the maximum allowed\nalowed receive size for the next message.\n\nBy sending a second message with a large value (>1420 bytes)\nthe attacker can then achieve a heap buffer overflow.\n\nThis fix replaces min_t(int, ...) with min_t(u32)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"56eab82fa6fb5ca024b0514e249d40d9b23ee5a7","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"a110dbe928561d440e9e117d17331139a0bedace","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"ceae058eb707ddd0d68f0872f9d9f23b7c30c37b","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"55abc475d096da4a5356b6efb0cfdc6156bc1550","versionType":"git"},{"version":"0626e6641f6b467447c81dd7678a69c66f7746cf","status":"affected","lessThan":"6b4f875aac344cdd52a1f34cc70ed2f874a65757","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/transport_rdma.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","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/transport_rdma.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c"},{"url":"https://git.kernel.org/stable/c/56eab82fa6fb5ca024b0514e249d40d9b23ee5a7"},{"url":"https://git.kernel.org/stable/c/a110dbe928561d440e9e117d17331139a0bedace"},{"url":"https://git.kernel.org/stable/c/ceae058eb707ddd0d68f0872f9d9f23b7c30c37b"},{"url":"https://git.kernel.org/stable/c/55abc475d096da4a5356b6efb0cfdc6156bc1550"},{"url":"https://git.kernel.org/stable/c/6b4f875aac344cdd52a1f34cc70ed2f874a65757"}],"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 ksmbd SMB Direct negotiation is reached by a remote peer over the network via the RDMA listener on SMB Direct ports such as 445/5445.\nAC:L - An attacker can trigger the bug with a crafted negotiation request followed by an oversized data-transfer message; no race or victim-controlled timing is required.\nPR:N - The vulnerable path runs during SMB Direct transport negotiation before SMB authentication or session setup, so no credentials or prior privileges are required.\nUI:N - No victim user action is needed beyond the server exposing ksmbd SMB Direct; the attacker sends network protocol messages directly.\nS:U - The impact is kernel memory corruption within the same host security authority, not a cross-scope escape such as guest-to-host or IOMMU boundary bypass.\nC:H - The signedness bug lets the attacker turn a small allocated receive buffer into a huge posted RDMA receive target, causing attacker-controlled kernel heap memory corruption that can plausibly be leveraged for information disclosure.\nI:H - The second SMB Direct message causes an out-of-bounds write/DMA overwrite into kernel heap memory, which is high-integrity impact and plausibly exploitable for control-flow or data corruption.\nA:H - The heap buffer overflow is remotely triggerable pre-authentication and can crash or panic the kernel even without full code execution."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:25:08.090Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.19.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}