CVE-2026-64530

Canonical Ubuntu Linux: use-after-free

Risk score: 79/100
CVSS: 9.8 v3.1
Published: 26 Jul 2026

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What to know

What it is: A critical vulnerability in the Linux kernel allows an attacker to cause a use-after-free (UAF) error, potentially leading to arbitrary code execution. An attacker could exploit this vulnerability to gain control over the system.
Affected: {'product': 'Ubuntu Linux', 'vendor': 'Canonical'}
Fix: Check the linked advisory for the fix, as no specific version is mentioned.
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-2026-64530: Use-after-free (CVSS 9.8)
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: Use-after-free (CWE-416). 400 other warnings in 30 days
Same product: Earlier Canonical Ubuntu Linux warnings. 163 in the last 90 days

Why it is Amber

CVSS 9.8 critical
Remotely exploitable without logging in
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: net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle tcf_classify() can return TC_ACT_CONSUMED while the skb is held by the defragmentation engine (e.g. act_ct on out-of-order fragments). When that happens the skb is no longer owned by the caller and must not be touched again. tcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the switch and returned the skb to the caller as if classification had passed. The only qdisc that wires up qevents today is RED, via three call sites (qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop) red_enqueue() was continuing to operate on an skb it no longer owns in this case -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF. tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10 tc filter add block 10 ... action ct (with ct defrag enabled and traffic that produces out-of-order fragments, e.g. a fragmented UDP stream) Handle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress and egress fast paths do: treat it as stolen and return NULL without touching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be dropped/freed here, as it is no longer owned by us.

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