Improper Update of Reference Count Affecting microvm-kernel package, versions <1:6.1.189-236.399.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.17% (7th percentile)

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  • Snyk IDSNYK-AMZN2023-MICROVMKERNEL-21813518
  • published29 Oct 2026
  • disclosed18 Oct 2026

Introduced: 18 Oct 2026

NewCVE-2026-98586  (opens in a new tab)
CWE-911  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 microvm-kernel to version 1:6.1.189-236.399.amzn2023 or higher.
This issue was patched in ALAS2023-2026-3336.

NVD Description

Note: Versions mentioned in the description apply only to the upstream microvm-kernel package and not the microvm-kernel package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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

sctp: hold asoc or transport before mod_timer() in timer handlers

Take the association or transport reference before rearming a timer in the timer handlers.

The existing code calls mod_timer() before taking the reference needed by the rearmed timer without holding the sock lock. This creates a race with timer cleanup: if the timer is deleted after mod_timer() returns but before the reference is taken, the cleanup path can drop the timer's reference and destroy the transport or association. The timer handler then takes a reference on the already freed object and eventually drops it, causing a refcount underflow.

Hold the object before mod_timer() and drop the reference if mod_timer() reports that the timer was already pending in timer handlers. Apply the same ordering to the proto-unreachable path, which can rearm a transport timer outside the timer handlers without holding the sock lock.

CVSS Base Scores

version 3.1