smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()
CVE-2026-89632 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 8.2 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89632?
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Who is affected
- Linux Linux: a158bb66b1373866d9fd5997565a58a573085539 to < b70bc592afd19732e2e4563300ebe8f974280365, 67ec9949b0dfe78c99e110dd975eb7dc5645630c to < 711cf71300d7992f450600df8864917d3538679f, 67ec9949b0dfe78c99e110dd975eb7dc5645630c to < 05f78e6cf34ea3a285053bd5999e08e8ac298bd5, 6.6.32 to < 6.6.160
- Linux Linux: 6.8
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()
reparse_buf_ptr() reads buf->ReparseDataLength before checking that
count covers the full fixed header:
buf = (struct reparse_data_buffer *)((u8 *)io + off);
len = sizeof(*buf); /* 8 bytes */
rdlen = le16_to_cpu(buf->ReparseDataLength); /* offset 4, 2 bytes */
if (count < len || count < rdlen + len) /* check comes after */
struct reparse_data_buffer has ReparseDataLength at offset 4. If a
server returns OutputCount < 6, the read at offset 4-5 reaches past
the end of the received data. The off+count bounds against iov_len
were already validated, but that does not protect against count being
smaller than sizeof(*buf).
Split the check: verify count >= sizeof(*buf) before reading
ReparseDataLength, then verify count covers the data region.
Check your whole app
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References
- git.kernel.org/stable/c/b70bc592afd19732e2e4563300ebe8f974280365
- git.kernel.org/stable/c/711cf71300d7992f450600df8864917d3538679f
- git.kernel.org/stable/c/05f78e6cf34ea3a285053bd5999e08e8ac298bd5
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON