CVE-2026-99274 is a vulnerability in Linux Kernel
Published on November 7, 2026
smb: client: fix fiemap wild read on empty truncated response
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix fiemap wild read on empty truncated response
smb3_fiemap() treats -E2BIG from SMB2_ioctl() as a truncated range blob
and loops for the next chunk. If the server reports
STATUS_BUFFER_OVERFLOW with OutputCount == 0, SMB2_ioctl() returns
-E2BIG with out_data == NULL and out_data_len == 0, and the existing
length checks accept the empty result. The loop then evaluates
next = out_data[num - 1].file_offset + ...
with num == 0, reading 16 bytes before NULL.
Reject a truncated range blob that contains no range, so the resume
offset is never computed from an empty response. Also require the last
range in a truncated blob to advance the resume offset without
overflowing, and to stay within the requested range; a malicious or
broken server could otherwise make no progress or underflow len and loop
forever. Free the previous response buffer before retrying.
Reproduced on 6.6.87.2 with a malicious SMB2 server that answers
FSCTL_QUERY_ALLOCATED_RANGES with STATUS_BUFFER_OVERFLOW and
OutputCount == 0; an FS_IOC_FIEMAP ioctl on the mount oopses in
cifs_fiemap() with CR2 = fffffffffffffff8. The code path is unchanged
on mainline.
Products Associated with CVE-2026-99274
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Affected Versions
Linux:- Version 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 and below 4a426ca5be7e3dedbe76575b967db04fbf01136f is affected.
- Version 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 and below 31f6dbb29fe17fa9595c7e8b19fd92915b03a4ca is affected.
- Version 2f3ebaba13cebd8badfb9aed31c0cf3cc82eb4f4 and below f5baa17a0f316c235d61623ac8e8fb32c2b3c0cc is affected.
- Version 5.2 is affected.
- Before 5.2 is unaffected.
- Version 6.18.61, <= 6.18.* is unaffected.
- Version 7.3.2, <= 7.3.* is unaffected.
- Version 7.4-rc1, <= * is unaffected.