CVE-2026-31609 smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
A double-free vulnerability in the Linux kernel SMB client allows attackers to cause denial of service or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31609?
CVE-2026-31609 is a critical use after free 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: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
smbd_send_batch_flush() already calls smbd_free_send_io(), so we should not call it again after smbd_post_send() moved it to the batch list.
Weakness: CWE-415
Which versions are affected by CVE-2026-31609?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31609?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-31609 being exploited?
There is no known exploitation of CVE-2026-31609 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83789, BELL-CVE-2026-31609, DEBIAN-CVE-2026-31609, GHSA-rc8c-94m4-frfh, ROOT-OS-DEBIAN-11-CVE-2026-31609, ROOT-OS-DEBIAN-12-CVE-2026-31609 and 2 more.