CVE-2026-74290
Received Received - Intake

Flow Classifier Kernel Pointer Exposure in Linux Kernel

Publication date: 2026-08-15

Last updated on: 2026-08-15

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: Dont expose folded kernel pointers The flow classifier falls back to addr_fold() for fields that are missing from packet headers. In map mode, userspace controls mask, xor, rshift, addend and divisor, and can observe the resulting classid through class statistics. This allows a tc classifier in a user/network namespace to recover the 32-bit folded value of skb->sk, skb_dst() or skb_nfct(). Align with standard kernel practices for pointer hashing and replace the XOR folding with a keyed siphash (which is cryptographically secure)

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Meta Information

Published
2026-08-15
Last Modified
2026-08-15
Generated
2026-08-15
AI Q&A
2026-08-15
EPSS Evaluated
N/A
NVD
CVE-2026-74290
EUVD
EUVD-2026-59437

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the flow classifier exposing folded kernel pointers through class statistics. When fields are missing from packet headers, it uses addr_fold() which can be manipulated by userspace in map mode to recover 32-bit folded values of sensitive kernel pointers like skb->sk, skb_dst(), or skb_nfct().

Detection Guidance

This vulnerability involves kernel pointer exposure through the flow classifier. Detection requires checking for suspicious use of tc (traffic control) commands in user/network namespaces that manipulate mask, xor, rshift, addend, or divisor parameters. Monitor for unusual classid values in tc statistics output.

Impact Analysis

An attacker in a user or network namespace could exploit this to leak kernel memory addresses, potentially aiding in further exploits or bypassing security mechanisms that rely on address space layout randomization.

Mitigation Strategies

Apply the latest Linux kernel update to patch this issue. Disable or restrict access to tc classifiers in untrusted namespaces. Review and audit any custom tc configurations for unusual parameters that could exploit this flaw.

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