CVE-2026-31538: smb: server: make use of smbdirect_socket.recv_io.credits.available

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-24 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: smb: server: make use of smbdirect_socket.recv_io.credits.available The logic off managing recv credits by counting posted recv_io and granted credits is racy. That's because the peer might already consumed a credit, but between receiving the incoming recv at the hardware and processing the completion in the 'recv_done' functions we likely have a window where we grant credits, which don't really exist. So we better have a decicated counter for the available credits, which will be incremented when we posted new recv buffers and drained when we grant the credits to the peer. This fixes regression Namjae reported with the 6.18 release.

Affected products

Linux kernel: from 6.18 before 6.18.11; from 6.19 before 6.19.1 — fixed in 6.18.11, 6.19.1

How to fix

Upgrade to a fixed version: Linux kernel 6.18.11, 6.19.1. Check the vendor advisory for mitigations.

References

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