CVE-2026-68462

Received Received - Intake

Buffer Pointer Negative Offset Validation Bypass in Linux Kernel

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject negative const offsets for buffer pointers The verifier rejects variable offsets for PTR_TO_TP_BUFFER and PTR_TO_BUF accesses, but it currently accepts a constant negative offset produced by pointer arithmetic. Commit 022ac0750883 ("bpf: use reg->var_off instead of reg->off for pointers") moved constant pointer offsets from reg->off to reg->var_off. However, __check_buffer_access() continued to check only the instruction offset. An access with reg->var_off equal to -8 and an instruction offset of zero therefore passes verification. For writable raw tracepoints, the access end is also calculated from the unsigned reg->var_off.value. An eight-byte access starting at -8 wraps the calculated end to zero, allowing the program to load and attach without increasing max_tp_access. After ensuring that reg->var_off is constant, calculate the effective access start using signed arithmetic and reject it when it is negative. Use the validated start to calculate the access end for both PTR_TO_TP_BUFFER and PTR_TO_BUF.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-68462

EUVD

EUVD-2026-59084

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 the BPF verifier incorrectly handling negative constant offsets for buffer pointers. The verifier rejects variable offsets but accepts constant negative offsets, allowing out-of-bounds memory access. This occurs because the verifier checks instruction offsets but not the effective access start calculated from reg->var_off, which can be negative.

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF (Berkeley Packet Filter) implementation and requires kernel-level inspection. Detection involves checking kernel logs for BPF-related errors or verifying if the kernel version includes the fix. Commands like 'dmesg | grep -i bpf' or 'uname -r' may help identify affected systems.

Impact Analysis

This vulnerability could allow a local attacker to escalate privileges or cause a denial of service by exploiting the BPF subsystem. It enables unauthorized memory access, potentially leading to system instability or security breaches if exploited.

Compliance Impact

The provided CVE data does not describe any direct impact on compliance with GDPR, HIPAA, or other standards. The vulnerability is specific to the Linux kernel's BPF verifier and involves buffer pointer offset validation. No evidence suggests it affects data protection, privacy, or security controls required by these regulations.

Mitigation Strategies

Apply the latest kernel patches or updates that include the fix for this BPF vulnerability. If patches are unavailable, consider disabling BPF or restricting unprivileged BPF usage via kernel parameters like 'kernel.unprivileged_bpf_disabled=1'.

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