CVE-2026-64496: iio: event: Fix event FIFO reset race
In the Linux kernel, the following vulnerability has been resolved:
iio: event: Fix event FIFO reset race
iioeventgetfd() creates the event file descriptor with anoninodegetfd(), which allocates a new fd, creates the anonymous file and installs it in the process fd table before returning to the caller.
The IIO code resets the event FIFO after anoninodegetfd() has returned, but before IIOGETEVENTFDIOCTL has copied the fd number to userspace. But since fd tables are shared between threads, another thread can guess the newly allocated fd number and issue a read() on it as soon as the fd has been installed.
This means the kfifotouser() in iioeventchrdevread() can run in parallel with the kfiforesetout() in iioeventgetfd().
The kfifo documentation says that kfiforesetout() is only safe when it is called from the reader thread and there is only one concurrent reader. Otherwise it is dangerous and must be handled in the same way as kfiforeset().
If that happens, kfifotouser() can advance the FIFO out index based on state from before the reset, after the reset has already moved the out index to the current in index. That can leave the FIFO with an out index past the in index. A later read() can then see an underflowed FIFO length and copy more data than the event FIFO buffer contains. This can result in an out-of-bounds read and leak adjacent kernel memory to userspace.
Move the FIFO reset before anoninodegetfd(). At that point the event fd is marked busy, but the new fd has not been installed yet, so userspace cannot access it while the FIFO is reset.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1011.11~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1011.11~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1~24.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-31.31 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1012.12 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1011.11 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1006.7 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2018.18 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1011.11 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Compensating control
In the Linux kernel IIO event code, move the FIFO reset in iio_event_getfd() to before anon_inode_getfd() is called, so the FIFO cannot be reset concurrently with a read on the newly installed file descriptor.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64496?
CVE-2026-64496 has a severity rating of 7.1 on the CVSS scale, indicating high severity.
How do I fix CVE-2026-64496?
To fix CVE-2026-64496, you should update the Linux kernel to the patched version that addresses this vulnerability.
What kind of systems are affected by CVE-2026-64496?
CVE-2026-64496 affects systems running vulnerable versions of the Linux kernel that utilize the IIO event FIFO.
Is CVE-2026-64496 exploitable remotely?
CVE-2026-64496 can be exploited locally, as it relates to the manipulation of event file descriptors in the Linux kernel.
What are the potential impacts of CVE-2026-64496?
Exploitation of CVE-2026-64496 can lead to denial of service due to the event FIFO reset race condition.