ksmbd: fix signededness bug in smb_direct_prepare_negotiation()
CVE-2026-43185 · published 6 May 2026
How serious is it
- Severity: critical, CVSS score 9.8 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-2026-43185?
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Who is affected
- Linux Linux: 0626e6641f6b467447c81dd7678a69c66f7746cf to < 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7, 0626e6641f6b467447c81dd7678a69c66f7746cf to < a110dbe928561d440e9e117d17331139a0bedace, 0626e6641f6b467447c81dd7678a69c66f7746cf to < ceae058eb707ddd0d68f0872f9d9f23b7c30c37b, 0626e6641f6b467447c81dd7678a69c66f7746cf to < 55abc475d096da4a5356b6efb0cfdc6156bc1550
- Linux Linux: 5.15
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:
ksmbd: fix signededness bug in smb_direct_prepare_negotiation()
smb_direct_prepare_negotiation() casts an unsigned __u32 value
from sp->max_recv_size and req->preferred_send_size to a signed
int before computing min_t(int, ...). A maliciously provided
preferred_send_size of 0x80000000 will return as smaller than
max_recv_size, and then be used to set the maximum allowed
alowed receive size for the next message.
By sending a second message with a large value (>1420 bytes)
the attacker can then achieve a heap buffer overflow.
This fix replaces min_t(int, ...) with min_t(u32)
Check your whole app
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References
- git.kernel.org/stable/c/56eab82fa6fb5ca024b0514e249d40d9b23ee5a7
- git.kernel.org/stable/c/a110dbe928561d440e9e117d17331139a0bedace
- git.kernel.org/stable/c/ceae058eb707ddd0d68f0872f9d9f23b7c30c37b
- git.kernel.org/stable/c/55abc475d096da4a5356b6efb0cfdc6156bc1550
- git.kernel.org/stable/c/6b4f875aac344cdd52a1f34cc70ed2f874a65757
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON