# CVE-2026-99272: smb: client: validate the data area in SMB2_read()

Status: published. Published: 2026-11-07. Updated: 2026-11-07.

In the Linux kernel, the following vulnerability has been resolved:

smb: client: validate the data area in SMB2_read()

SMB2_read() copies le32_to_cpu(rsp->DataLength) bytes from
(char *)rsp + rsp->DataOffset without checking that the range lies
within the response actually received. A READ response with
DataOffset == 0 makes smb2_get_data_area_len() zero the data length, so
smb2_check_message() accepts a frame as short as the fixed response,
while SMB2_read() still uses the server-supplied DataLength, capped only
by CIFS_MAX_MSGSIZE and the caller's length.

A malicious server can answer the synchronous read used by the
mfsymlinks (or SFU) symlink parser with an 81-byte READ response
carrying DataOffset 0 and DataLength 1067, making the client copy 1067
bytes from a 448-byte receive object (KASAN slab-out-of-bounds; up to
16 KiB in the general case).

Clamp a zero (or header-overlapping) DataOffset to read_rsp_size, as
handle_read_data() does for the asynchronous path, and reject the
response unless DataOffset + DataLength fits within rsp_iov.iov_len.
The SMB1 helper was fixed the same way in 5be5bdda5863.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ d8e050398d23ef7c019c96200b80d73f4e5cec0c; < 1ba1937de005e261a8858f45bfef5da7458df94c (affected, git); ≥ d8e050398d23ef7c019c96200b80d73f4e5cec0c; < 2ec9cdf469dd32bcf33073aeb30c08e9356e0ca1 (affected, git). Source: CNA: Linux
- Linux / Linux: 3.7 (affected); ≥ 0; < 3.7 (unaffected, semver); ≥ 7.3.2; ≤ 7.3.* (unaffected, semver); ≥ 7.4-rc1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/1ba1937de005e261a8858f45bfef5da7458df94c (CNA: Linux)

- https://git.kernel.org/stable/c/2ec9cdf469dd32bcf33073aeb30c08e9356e0ca1 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-99272; retrieved 2026-11-07; source updated 2026-11-07

Revision: 3906e3dd3f8164bc36d9ae5cbd1ab815aa6ce298aa3506d3d21639ef9e696ac7

Canonical: https://y2.dev/cve/CVE-2026-99272

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