Race Condition Affecting microvm-kernel package, versions <1:6.1.189-236.399.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.18% (8th percentile)

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  • Snyk IDSNYK-AMZN2023-MICROVMKERNEL-21814528
  • published29 Oct 2026
  • disclosed18 Oct 2026

Introduced: 18 Oct 2026

NewCVE-2026-98624  (opens in a new tab)
CWE-366  (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:

netfilter: nfnetlink_queue: hold nfnl mutex in event notifier

We must serialize the release notifier and the config netlink function. A concurrent thread can issue close() which can call the release function while unrelated socket processes UNBIND request for same portid:

Oops: general protection fault, [..] RIP: 0010:__instance_destroy+0x60/0x210 [nfnetlink_queue] Call Trace: nfqnl_recv_config+0x9b0/0xdc0 [nfnetlink_queue] nfnetlink_rcv_msg+0x7c2/0xeb0 ? __pfx_nfnetlink_rcv_msg+0x10/0x10

After this, parallel UNBIND and URELEASE events are impossible.

This change isn't nice, but its the shortest fix given instances are not refcounted and the nfnetlink config callback drops the rcu read lock early due to need for sleeping allocations.

CVSS Base Scores

version 3.1