{"id":"CVE-2026-99274","title":"smb: client: fix fiemap wild read on empty truncated response","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix fiemap wild read on empty truncated response\n\nsmb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob\nand loops for the next chunk. If …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < 4a426ca5be7e3dedbe76575b967db04fbf01136f","Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < 31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca","Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc","Linux 5.2"],"published":"2026-11-07","updated":"2026-11-07","sourceUpdated":"2026-11-07T14:08:45.924Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99274","references":[{"url":"https://git.kernel.org/stable/c/4a426ca5be7e3dedbe76575b967db04fbf01136f"},{"url":"https://git.kernel.org/stable/c/31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca"},{"url":"https://git.kernel.org/stable/c/f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc"}],"tags":["cve.org"],"ingestedAt":"2026-11-07T14:18:21.462Z","slug":"CVE-2026-99274","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix fiemap wild read on empty truncated response\n\nsmb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob\nand loops for the next chunk. If the server reports\nSTATUS_BUFFER_OVERFLOW with OutputCount == 0, SMB2_ioctl() returns\n-E2BIG with out_data == NULL and out_data_len == 0, and the existing\nlength checks accept the empty result. The loop then evaluates\n\n\tnext = out_data[num - 1].file_offset + ...\n\nwith num == 0, reading 16 bytes before NULL.\n\nReject a truncated range blob that contains no range, so the resume\noffset is never computed from an empty response. Also require the last\nrange in a truncated blob to advance the resume offset without\noverflowing, and to stay within the requested range; a malicious or\nbroken server could otherwise make no progress or underflow len and loop\nforever. Free the previous response buffer before retrying.\n\nReproduced on 6.6.87.2 with a malicious SMB2 server that answers\nFSCTL_QUERY_ALLOCATED_RANGES with STATUS_BUFFER_OVERFLOW and\nOutputCount == 0; an FS_IOC_FIEMAP ioctl on the mount oopses in\ncifs_fiemap() with CR2 = fffffffffffffff8. The code path is unchanged\non mainline.\n\n## Affected\n\n- `Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < 4a426ca5be7e3dedbe76575b967db04fbf01136f`\n- `Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < 31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca`\n- `Linux >= 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 < f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc`\n- `Linux 5.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}