Description
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.
Published: 2026-11-07
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Sat, 07 Nov 2026 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-126

Sat, 07 Nov 2026 14:15:00 +0000

Type Values Removed Values Added
Description 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.
Title smb: client: fix fiemap wild read on empty truncated response
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-11-07T14:08:45.924Z

Reserved: 2026-09-25T10:25:14.405Z

Link: CVE-2026-99274

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-07T14:17:02.730

Modified: 2026-11-07T14:17:02.730

Link: CVE-2026-99274

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-07T16:00:17Z

Weaknesses