CVE-2026-64383 smb: client: fix double-free in SMB2_flush() replay

What is CVE-2026-64383?

CVE-2026-64383 is a critical use after free vulnerability in Linux kernel, published on 25 Jul 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: fix double-free in SMB2_flush() replay

SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time.

Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.

Weakness: CWE-415

Which versions are affected by CVE-2026-64383?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-64383?

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-2026-64383 being exploited?

There is no known exploitation of CVE-2026-64383 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 AZL-93734, BELL-CVE-2026-64383, DEBIAN-CVE-2026-64383, GHSA-j3g4-c7cw-5ch7, ROOT-OS-UBUNTU-2204-CVE-2026-64383, UBUNTU-CVE-2026-64383.