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

What is CVE-2026-31538?

CVE-2026-31538 is a high-severity vulnerability in Linux kernel, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Which versions are affected by CVE-2026-31538?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-31538?

Apply the vendor's patch.

Is CVE-2026-31538 being exploited?

There is no known exploitation of CVE-2026-31538 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-31538, DEBIAN-CVE-2026-31538, GHSA-f5hg-hrh7-wfrr, UBUNTU-CVE-2026-31538.