CVE-2026-43185: ksmbd: fix signededness bug in smb_direct_prepare_negotiation()
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix signededness bug in smbdirectpreparenegotiation()
smbdirectpreparenegotiation() casts an unsigned u32 value from sp->maxrecvsize and req->preferredsendsize to a signed int before computing mint(int, ...). A maliciously provided preferredsendsize of 0x80000000 will return as smaller than maxrecvsize, 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 mint(int, ...) with mint(u32)
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.19.6-1 - Compensating control
In ksmbd's smb_direct_prepare_negotiation(), replace min_t(int, ...) with min_t(u32, ...) when computing the minimum of sp->max_recv_size and req->preferred_send_size.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-43185?
CVE-2026-43185 has been classified with a medium severity level due to its potential to cause issues in the smb_direct_prepare_negotiation function.
How do I fix CVE-2026-43185?
To fix CVE-2026-43185, update your Linux kernel to the latest stable version which contains the patched code.
What systems are affected by CVE-2026-43185?
CVE-2026-43185 affects systems running the Linux kernel with ksmbd, particularly those using SMB direct.
What kind of vulnerability is CVE-2026-43185?
CVE-2026-43185 is a signedness bug that impacts the proper functioning of the smb_direct_prepare_negotiation function.
What is the impact of CVE-2026-43185 on system security?
The impact of CVE-2026-43185 can lead to unexpected behaviors in file sharing over SMB if exploited.