CVE-2026-23204
Modified Modified - Updated After Analysis
Buffer Overflow in Linux Kernel cls_u32 Causes KASAN Crash

Publication date: 2026-02-14

Last updated on: 2026-06-01

Assigner: kernel.org

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
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Meta Information
Published
2026-02-14
Last Modified
2026-06-01
Generated
2026-06-16
AI Q&A
2026-02-14
EPSS Evaluated
2026-06-15
NVD
CVE-2026-23204
EUVD
EUVD-2026-5841
Affected Vendors & Products
Showing 17 associated CPEs
Vendor Product Version / Range
linux linux_kernel 2.6.35
linux linux_kernel 2.6.35
linux linux_kernel 2.6.35
linux linux_kernel 2.6.35
linux linux_kernel 2.6.35
linux linux_kernel 2.6.35
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 6.7 (inc) to 6.12.70 (exc)
linux linux_kernel 6.19
linux linux_kernel From 6.13 (inc) to 6.18.10 (exc)
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 2.6.35.1 (inc) to 6.6.124 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-125 The product reads data past the end, or before the beginning, of the intended buffer.
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Executive Summary

This vulnerability exists in the Linux kernel's network scheduler component, specifically in the cls_u32 classifier. The issue arises because the function skb_header_pointer() does not properly validate negative offset values, which can lead to out-of-bounds memory access.

The fix involved replacing skb_header_pointer() with skb_header_pointer_careful(), which performs more thorough validation of the offset values to prevent such errors.

The vulnerability was reported by GangMin Kim, who also provided a reproduction method that fools the u32_classify() function, causing a kernel slab-out-of-bounds bug detected by KASAN (Kernel Address Sanitizer).

Impact Analysis

This vulnerability can lead to out-of-bounds memory access within the Linux kernel's network scheduler, which may cause system instability, crashes, or potentially allow an attacker to execute arbitrary code or escalate privileges.

Since the issue involves kernel memory corruption, it could be exploited to compromise the security and reliability of affected systems.

Compliance Impact

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