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CVE-2026-97563smb: client: reject out-of-bounds DataOffset in CIFSSMBRead()

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject out-of-bounds DataOffset in CIFSSMBRead() The SMB1 synchronous read helper CIFSSMBRead() validates the server's DataLength against CIFSMaxBufSize and the caller's count, but never validates DataOffset. The copy source is formed as &pSMBr->hdr.Protocol + le16_to_cpu(pSMBr->DataOffset) and memcpy()'d for DataLength bytes with no check that the [DataOffset, DataOffset + DataLength) range lies within the response actually received from the server. A malicious or compromised SMB1 server can return a response carrying an in-range DataLength and a large DataOffset, driving the source pointer past the end of the response buffer. The memcpy() then copies adjacent kernel heap into the caller's read buffer (information disclosure), or reads unmapped memory and oopses (denial of service). SMB1 is not negotiated by default; reaching this code requires an explicit vers=1.0 mount. Both DataOffset and the received response length recorded in rsp_iov.iov_len are relative to the start of the SMB header, so reject the response unless DataOffset + DataLength fits within that length, using overflow-safe arithmetic, before forming the source pointer. The response length has been validated by the previous patch, so the DataOffset and DataLength fields can be read safely here. While here, make data_length unsigned. It holds a length derived from unsigned on-the-wire fields and is only ever compared against unsigned quantities; print it with %u accordingly, and add __func__ to the cifs_dbg() calls in this function.

Timeline

  1. ID reserved

    By Linux

  2. · 1 day later

    Published

  3. · 24 days later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)
0.19% · top 91% of all CVEs (13 Nov 2026)
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The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

  • Linux · Linux

    • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 667feba13e78d16393aacb15869f70970f422227
    • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 5be5bdda5863eacc964b609ba927764f253431b3

  • Linux · Linux

    • affected 2.6.12
    • unaffected < 2.6.12
    • unaffected 7.2.7 – ≤ 7.2.*
    • unaffected 7.3 – ≤ *

References

References2

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .