CVE-2026-23204 net/sched: cls_u32: use skb_header_pointer_careful()
A slab-out-of-bounds read in the Linux kernel's u32 classifier allows attackers to cause denial of service or potentially execute code 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-2026-23204?
CVE-2026-23204 is a high-severity memory corruption vulnerability in Linux kernel, published on 14 Feb 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: cls_u32: use skb_header_pointer_careful()
skb_header_pointer() does not fully validate negative @offset values.
Use skb_header_pointer_careful() instead.
GangMin Kim provided a report and a repro fooling u32_classify():
BUG: KASAN: slab-out-of-bounds in u32_classify+0x1180/0x11b0 net/sched/cls_u32.c:221
Weakness: CWE-125
Which versions are affected by CVE-2026-23204?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23204?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-23204 being exploited?
There is no known exploitation of CVE-2026-23204 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-77658, BELL-CVE-2026-23204, DEBIAN-CVE-2026-23204, GHSA-rf63-9f5h-hhg6, ROOT-OS-DEBIAN-11-CVE-2026-23204, ROOT-OS-DEBIAN-12-CVE-2026-23204 and 4 more.