CVE-2026-64561

Canonical Ubuntu Linux: race condition

Risk score: 72/100
CVSS: 8.8 v3.1
Exploit chance (30 days): 0.3%
Published: 4 Aug 2026

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What to know

What it is: A high-severity vulnerability in the Linux kernel's KVM module allows an attacker to potentially gain elevated privileges. An attacker could exploit this vulnerability to gain control over the system.
Affected: {'product': 'Ubuntu Linux', 'vendor': 'Canonical'}
Fix: Check the linked advisory for details on the fix.
Exploitation: No known exploitation

Story map

Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

Canonical Ubuntu Linux: Red, act today. A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable. An unauthenticated attacker can exploit this vulnerability by sending crafted HTTP requests, causing a heap buffer overflow in the NGINX worker process leading to a restart, or potential…

The flaws

CVE-2026-64561: Race condition (CVSS 8.8 · EPSS 0%)
CVE-2026-93479: Heap buffer overflow can lead to remote code execution (CVSS 8.1 · EPSS 1%)
CVE-2026-15176: Heap buffer overflow can lead to remote code execution (CVSS 8.1 · EPSS 1%)
CVE-2026-97205: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_core_module module (CVSS 8.1 · EPSS 1%)

The fix

Fix: Check the linked advisory for the concrete fix.

Who is exposed: {'products': ['NGINX Plus', 'NGINX Open Source'], 'packages': [], 'versions': []}

Where it stands

No known exploitation

How it unfolded

26 Oct, Ubuntu security notices (official): USN-8955-1: nginx vulnerabilities
5 Nov, Ubuntu security notices (official): USN-8955-2: nginx vulnerabilities
6 Nov, Ubuntu security notices (official): USN-9003-1: Linux kernel (NVIDIA) vulnerabilities

Connects to

Same weakness: Race condition (CWE-362). 143 other warnings in 30 days
Same product: Earlier Canonical Ubuntu Linux warnings. 147 in the last 90 days

Why it is Amber

CVSS 8.8 high
On your watchlist: linux kernel
Named in a government or vendor bulletin

Government and vendor bulletins

USN-9003-1: Linux kernel (NVIDIA) vulnerabilities

References

Original description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately.

Last activity 6 Nov 2026. Patch Forecast updates every hour.