CVE-2026-98540
Received Received - Intake

fprobe Double Execution in Linux Kernel

Vulnerability report for CVE-2026-98540, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-10-18

Last updated on: 2026-10-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: fprobe: Terminate the fgraph_data list when the reservation is not filled fprobe_fgraph_entry() reserves shadow stack space for every fprobe with an exit handler, but only fills it for those whose entry handler returns 0. fgraph_reserve_data() does not clear the area, so fprobe_return() parses the unused tail as headers left over from an earlier call, and an exit handler can run twice or despite its entry handler asking to skip it. Write a zero word after the last entry to terminate the walk. A zeroed slot does not decode to a NULL fprobe on the arches that encode the header into one unsigned long, since arch_decode_fprobe_header_fp() ORs in FPROBE_HEADER_MSB_PATTERN, so make read_fprobe_header() return NULL for a zeroed slot.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-19
Generated
2026-10-19
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
Linux Linux e0a384434ae1bdfb03954c46c464e3dbd3223ad6
Linux Linux e0a384434ae1bdfb03954c46c464e3dbd3223ad6
Linux Linux 7.1

Helpful Resources

Exploitability

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CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of fgraph_data list termination in the fprobe component. When fprobe_fgraph_entry() reserves shadow stack space but only fills it for certain cases, fgraph_reserve_data() fails to clear unused areas. This causes fprobe_return() to misinterpret leftover data as valid headers, leading to exit handlers executing incorrectly, such as running twice or being skipped despite entry handler requests.

Detection Guidance

This vulnerability is specific to the Linux kernel's fprobe component and requires kernel-level inspection. Detection involves checking kernel logs for fprobe-related errors or examining kernel memory for corrupted fgraph_data structures. Commands like dmesg, journalctl -k, or inspecting /proc/kallsyms may help identify issues. No standard network commands apply.

Impact Analysis

This vulnerability could allow attackers to manipulate kernel behavior by causing exit handlers to execute unintendedly or skip intended executions. This might lead to system instability, privilege escalation, or unauthorized access depending on the affected fprobe configurations and kernel modules.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a kernel-level issue related to fprobe shadow stack handling, which could lead to incorrect execution of exit handlers but does not inherently impact data protection or privacy requirements.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves this issue. If immediate patching is not possible, disable fprobe or any kernel modules relying on fgraph_data until the fix is applied. Monitor kernel logs for signs of exploitation or instability.

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