CVE-2026-23270 net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks
A use-after-free vulnerability in the Linux kernel's net/sched subsystem allows attackers to execute arbitrary code or escalate privileges via crafted network packets.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23270?
CVE-2026-23270 is a high-severity use after free vulnerability in Linux kernel, published on 18 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks
As Paolo said earlier [1]:
"Since the blamed commit below, classify can return TC_ACT_CONSUMED while the current skb being held by the defragmentation engine. As reported by GangMin Kim, if such packet is that may cause a UaF when the defrag engine later on tries to tuch again such packet."
act_ct was never meant to be used in the egress path, however some users are attaching it to egress today [2]. Attempting to reach a middle ground, we noticed that, while most qdiscs are not handling TC_ACT_CONSUMED, clsact/ingress qdiscs are. With that in mind, we address the issue by only allowing act_ct to bind to clsact/ingress qdiscs and shared blocks. That way it's still possible to attach act_ct to egress (albeit only with clsact).
[1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/ [2] https://lore.kernel.org/netdev/cc6bfb4a-4a2b-42d8-b9ce-7ef6644fb22b@ovn.org/
Weakness: CWE-416
Which versions are affected by CVE-2026-23270?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23270?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-23270 being exploited?
There is no known exploitation of CVE-2026-23270 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23270, DEBIAN-CVE-2026-23270, GHSA-62jp-jvc3-7hh9, ROOT-OS-DEBIAN-12-CVE-2026-23270, ROOT-OS-DEBIAN-13-CVE-2026-23270, ROOT-OS-UBUNTU-2204-CVE-2026-23270 and 2 more.