CVE-2026-43185
Analyzed Analyzed - Analysis Complete
Heap Buffer Overflow in Linux Kernel ksmbd

Publication date: 2026-05-06

Last updated on: 2026-05-11

Assigner: kernel.org

Description
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)
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Meta Information
Published
2026-05-06
Last Modified
2026-05-11
Generated
2026-06-16
AI Q&A
2026-05-06
EPSS Evaluated
2026-06-15
NVD
CVE-2026-43185
EUVD
EUVD-2026-27748
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
linux linux_kernel 7.0
linux linux_kernel From 6.19 (inc) to 6.19.6 (exc)
linux linux_kernel From 5.15 (inc) to 6.18.16 (exc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-674 The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
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Executive Summary

This vulnerability exists in the Linux kernel's ksmbd component, specifically in the smb_direct_prepare_negotiation() function. The issue arises because the function casts unsigned 32-bit values to signed integers before comparing them, which leads to incorrect comparisons when a maliciously crafted preferred_send_size value of 0x80000000 is used.

Due to this incorrect casting, the function incorrectly determines the minimum size, allowing an attacker to set a maximum allowed receive size that is too large. By sending a second message with a size greater than 1420 bytes, the attacker can trigger a heap buffer overflow.

The vulnerability was fixed by replacing the signed integer comparison with an unsigned 32-bit comparison to correctly handle the values.

Impact Analysis

This vulnerability can allow an attacker to cause a heap buffer overflow in the Linux kernel's ksmbd service. A heap buffer overflow can lead to memory corruption, which may be exploited to execute arbitrary code, cause a denial of service (system crash), or escalate privileges on the affected system.

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