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Linux Kernel: Out-of-Bounds Access in u32_classify Function
CVE-2026-23204
Summary
A security issue was found in the Linux kernel's u32_classify function. This issue allows an attacker to potentially access memory outside of the allowed range, potentially leading to a system crash. This issue has been fixed in a recent Linux kernel update, and administrators should ensure they have the latest version installed to prevent exploitation.
Original title
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...
Original 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
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
Published: 14 Feb 2026 · Updated: 10 Mar 2026 · First seen: 6 Mar 2026