CVE-2026-64409 Bluetooth: btmtksdio: fix infinite loop in btmtksdio_txrx_work()

What is CVE-2026-64409?

CVE-2026-64409 is a medium-severity denial of service vulnerability in Linux kernel, published on 25 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: btmtksdio: fix infinite loop in btmtksdio_txrx_work()

Every once in a while we see a hung btmtksdio_flush() task:

INFO: task kworker/u17:0:189 blocked for more than 122 seconds. __cancel_work_timer+0x3f4/0x460 cancel_work_sync+0x1c/0x2c btmtksdio_flush+0x2c/0x40 hci_dev_open_sync+0x10c4/0x2190 [..]

It all boils down to incorrect time_is_before_jiffies() usage in btmtksdio_txrx_work(). The btmtksdio_txrx_work() loop is expected to be terminated if running for longer than 5*HZ. However the timeout check is twisted: time_is_before_jiffies(old_jiffies + 5*HZ) evaluates to true when old_jiffies + 5*HZ is in the past i.e. when a timeout has occurred. Using OR with time_is_before_jiffies(txrx_timeout) means that: - before the 5-second timeout: the condition is `int_status || false`, so it loops as long as there are pending interrupts. - after the 5-second timeout: the condition becomes `int_status || true`, which is always true.

When the loop becomes infinite btmtksdio_txrx_work() loop never terminates and never releases the SDIO host.

Fix loop termination condition to actually enforce a 5*HZ timeout.

Weakness: CWE-835

Which versions are affected by CVE-2026-64409?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-64409?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-64409 being exploited?

There is no known exploitation of CVE-2026-64409 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-93518, BELL-CVE-2026-64409, DEBIAN-CVE-2026-64409, GHSA-x8qw-hc9f-qxq2, ROOT-OS-UBUNTU-2204-CVE-2026-64409, UBUNTU-CVE-2026-64409.