CVE-2026-99227: Linux Vulnerability (CVSS 7.8)

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/waitid: prevent cancel reference wrap io_waitid packs the cancellation state into bit 31 of ->refs and uses bits 30:0 as a 31-bit reference counter: #define IO_WAITID_CANCEL_FLAG BIT(31) #define IO_WAITID_REF_MASK GENMASK(30, 0) __io_waitid_cancel() marks a request canceled, then increments the low bits of ->refs to claim completion ownership. When another path owns the request, the increment remains even though cancellation returns false. The request remains discoverable by cancellation, so repeated failed attempts can wrap the 31-bit reference field to zero. A later cancellation can claim ownership and complete the request a second time. Use atomic_fetch_or() when setting the cancel flag and inspect the old flag value. The first cancel attempt continues to the existing ownership increment, preserving its wake and issuer handoff semantics. Later attempts see the cancel flag and return without incrementing the reference field. This makes repeated failed cancellation attempts idempotent while leaving the first-cancel state transitions unchanged.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.12%

1.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= f31ecf671ddc498f20219453395794ff2383e06b, < 20b67288574c7c3df6b8ea7ed3b7af90a868006f; >= f31ecf671ddc498f20219453395794ff2383e06b, < 5bfeee1774791602a0d53eb717f00f172127a017; >= f31ecf671ddc498f20219453395794ff2383e06b, < 857aa2012b91cad6fdef54a4b6c632d9d0b6e64f; >= f31ecf671ddc498f20219453395794ff2383e06b, < 22fb4a4518e305164c7f203608287564de292f34; >= f31ecf671ddc498f20219453395794ff2383e06b, < 98787d3fa4e99564d2b2bc21255b21f670c450d0
Linux	Linux	6.7

References

Timeline

Published: Nov 2, 2026
Last Modified: Nov 3, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-99227?

In the Linux kernel, the following vulnerability has been resolved: io_uring/waitid: prevent cancel reference wrap io_waitid packs the cancellation state into bit 31 of ->refs and uses bits 30:0 as a 31-bit reference counter: #define IO_WAITID_CANCEL_FLAG BIT(31) #define IO_WAITID_REF_MASK GENMASK(30, 0) __io_waitid_cancel() marks a request canceled, then increments the low bits of ->refs to claim completion ownership. When another path owns the request, the increment remains even though cancellation returns false. The request remains discoverable by cancellation, so repeated failed attempts can wrap the 31-bit reference field to zero. A later cancellation can claim ownership and complete the request a second time. Use atomic_fetch_or() when setting the cancel flag and inspect the old flag value. The first cancel attempt continues to the existing ownership increment, preserving its wake and issuer handoff semantics. Later attempts see the cancel flag and return without incrementing the reference field. This makes repeated failed cancellation attempts idempotent while leaving the first-cancel state transitions unchanged.

How severe is CVE-2026-99227?

CVE-2026-99227 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.12% probability of exploitation in the next 30 days.

How do I fix CVE-2026-99227?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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