CVE-2026-98033

Received Received - Intake

BPF Inner Map Identity Preservation Flaw

Publication date: 2026-09-25

Last updated on: 2026-10-15

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Preserve inner map identity in callback frames Callback frame constructors initialize map-typed argument registers with __mark_reg_known_zero() and then restore map_ptr. This clears map_uid, which is the only field distinguishing inner maps that share an inner_map_meta template. When a timer callback invokes bpf_for_each_map_elem() on a second inner map, both the saved first map and the second map value can reach the nested callback as the same template with map_uid zero. bpf_timer_init() then accepts pairing the timer from the second map with the first map. The runtime records the first map in the timer without taking a reference. Freeing that map does not find the timer stored in the second map, so a later timer callback dereferences the freed map. Copy map_uid from the same caller register as map_ptr when constructing for-each, timer/workqueue, and task-work callback arguments. The existing identity check can then reject mismatched inner maps while allowing a callback value to be paired with its actual map.

CVSS Scores

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Meta Information

Published

2026-09-25

Last Modified

2026-10-15

Generated

2026-10-15

AI Q&A

2026-09-25

EPSS Evaluated

2026-10-14

NVD

CVE-2026-98033

EUVD

EUVD-2026-86686

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a flaw in how callback frames handle inner maps. When constructing callback frames, map-typed arguments are incorrectly initialized, clearing a unique identifier (map_uid) that distinguishes inner maps sharing the same template. This can lead to mismatched inner maps being paired with timers, causing a timer callback to dereference a freed map and potentially crash the system.

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF (Berkeley Packet Filter) subsystem and requires kernel-level inspection. Detection involves checking kernel logs for BPF-related errors or examining loaded BPF programs and maps for inconsistencies. Commands like dmesg, journalctl -k, or bpftrace may help identify unusual BPF behavior. However, no direct detection commands are provided in the context.

Impact Analysis

This vulnerability could allow an attacker to cause a denial-of-service (DoS) condition by triggering a system crash. If exploited, it may lead to kernel panic, data corruption, or unauthorized access depending on the system configuration and privileges involved.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it is a technical flaw in the Linux kernel's BPF subsystem. Compliance impacts would depend on system-specific usage and mitigations rather than the vulnerability itself.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve this vulnerability. Monitor kernel security advisories for patches addressing CVE-2026-98033.

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