CVE-2026-98631
Received Received - Intake

Linux Kernel XSK Map Bounds Check Bypass

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: xsk: Use a 32-bit compare in xsk_map_gen_lookup xsk_map_gen_lookup() loads a u32 key and compares it with max_entries using BPF_JMP_IMM. BPF immediates are sign-extended to 64 bits, so a max_entries value of 0x80000000 or higher becomes a threshold larger than every zero-extended 32-bit key. An out-of-range index then skips the bounds check and the generated lookup reads past xsk_map[]. Compare with BPF_JMP32_IMM so the check stays in 32-bit unsigned range.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98631
EUVD
EUVD-2026-103545

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux e65650f291ee72fc578d6346080fc4699204ef2c
Linux Linux 5.5

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Exploitability

CWE
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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 a bounds check issue in the xsk_map_gen_lookup function. It occurs because BPF immediates are sign-extended to 64 bits, causing a 32-bit key comparison to fail when max_entries is 0x80000000 or higher. This allows an out-of-range index to bypass bounds checking, leading to reading past the xsk_map array.

Detection Guidance

This vulnerability is specific to the Linux kernel's XSK (AF_XDP) subsystem. Detection requires checking kernel version and XSK-related configurations. Use uname -a to verify kernel version and grep for XSK in /proc/kallsyms or dmesg logs for signs of exploitation.

Impact Analysis

This vulnerability could allow an attacker to read memory outside the intended bounds of the xsk_map array. This may lead to information disclosure, memory corruption, or potential privilege escalation if exploited. Systems using the affected Linux kernel component are at risk.

Mitigation Strategies

Apply the latest kernel patches from your Linux distribution. If patches are unavailable, disable AF_XDP sockets by setting netdev_max_backlog to 0 or unloading the xsk kernel module. Monitor system logs for unusual activity.

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