CVE-2026-89751
Published Sep 11, 2026
Modified Sep 14, 2026
Description
In the Linux kernel, the following vulnerability has been resolved: x86/tdx: Fix off-by-one in port I/O handling handle_in() and handle_out() in arch/x86/coco/tdx/tdx.c use: u64 mask = GENMASK(BITS_PER_BYTE * size, 0); GENMASK(h, l) includes bit h. For size=1 (INB), this produces GENMASK(8, 0) = 0x1FF (9 bits) instead of GENMASK(7, 0) = 0xFF (8 bits). The mask is one bit too wide for all I/O sizes. Fix the mask calculation.
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EPSS — Exploit Prediction
0.0017
Probability of exploitation
0.07%
Percentile rank
EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.
References
Other References
https://git.kernel.org/stable/c/0f63e656b1c679d32ac595de29d10c03efca6a25
https://git.kernel.org/stable/c/220011fe95fc78b2bc2d7d43893bc73957a5c811
https://git.kernel.org/stable/c/222b7005e4519f633b4cd666226256abbab46a1a
https://git.kernel.org/stable/c/bb45f705c4440dd3c689328319b88dd28770bbb8
https://git.kernel.org/stable/c/c4a22154870813d10aa0b4c734a574c726f9d4b0
https://git.kernel.org/stable/c/c6875423ad849ac234ab9812eb72f37ff8a490b4
Frequently Asked Questions
What is CVE-2026-89751? +
In the Linux kernel, the following vulnerability has been resolved:
x86/tdx: Fix off-by-one in port I/O handling
handle_in() and handle_out() in arch/x86/coco/tdx/tdx.c use:
u64 mask = GENMASK(BITS_PER_BYTE * size, 0);
GENMASK(h, l) includes bit h. For size=1 (INB), this produces
GENMASK(8, 0) = 0x1FF (9 bits) instead of GENMASK(7, 0) = 0xFF (8
bits). The mask is one bit too wide for all I/O sizes.
Fix the mask calculation.
How do I check if I'm vulnerable to CVE-2026-89751? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.