# CVE-2026-43185: ksmbd: fix signededness bug in smb_direct_prepare_negotiation()

CVE-2026-43185 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-43185, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-43185
- Priority: High
- CVSS: 9.8 (Moderate)
- EPSS: 0.0089
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 6, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43185

## 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)

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-43185](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43185.md) | May 15, 2026 |
| Linux | linux Debian 14 | 6.19.6-1 | [DEBIAN-CVE-2026-43185](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43185.md) | May 15, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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