CVE-2026-98048
Received Received - Intake

BPF Fastcall Pattern Rewrite Bypass in Linux Kernel

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: bpf: don't rewrite bpf_fastcall patterns entered by a jump mark_fastcall_pattern_for_call() must ensure that matched "spill; call; fill" instruction series is not interrupted by a jump. Otherwise the rewrite applied by bpf_remove_fastcall_spills_fills() is not sound. Record the instructions targeted by jumps in insn_aux_data[*].jump_target when the CFG is built and use this flag to stop growing a pattern at such an instruction. Jumps to the first spill are fine. Note that existing insn_aux_data[*].jmp_point field can't be reused, as it marks subprogram return instructions.

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-98048
EUVD
EUVD-2026-86701

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 incorrect handling of BPF (Berkeley Packet Filter) fastcall patterns when interrupted by a jump instruction. The system fails to properly track jumps during control flow graph (CFG) construction, leading to unsound rewrites of spill-fill instruction sequences by bpf_remove_fastcall_spills_fills().

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF (Berkeley Packet Filter) implementation. Detection requires checking the kernel version and BPF-related components for the presence of the described issue. Use commands like uname -a to check kernel version and inspect BPF-related logs or system traces for anomalies.

Impact Analysis

This vulnerability could allow attackers to manipulate BPF programs, potentially leading to unauthorized memory access, privilege escalation, or denial of service in systems running vulnerable Linux kernels.

Mitigation Strategies

Immediate mitigation involves updating the Linux kernel to a patched version that resolves this issue. Check your distribution's security advisories for kernel updates. If no patch is available, consider disabling BPF functionality temporarily if not required, or restrict access to BPF operations via kernel parameters or security modules.

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