CVE-2026-63830
Received Received - Intake

Heap Overflow in Linux Kernel via sk_msg Transform

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: skmsg: preserve sg.copy across SG transforms The sk_msg sg.copy bitmap is part of the scatterlist entry ownership state. A set bit tells sk_msg_compute_data_pointers() not to expose the entry through writable BPF ctx->data. This protects entries backed by pages that are not private to the sk_msg, such as splice-backed file page-cache pages. Several sk_msg transform paths move, copy, split, or compact msg->sg.data[] entries without moving the matching sg.copy bit. This can make an externally backed entry arrive at a new slot with a clear copy bit. A later SK_MSG verdict can then expose sg_virt(sge) as writable ctx->data and BPF stores can modify the original page cache. Keep sg.copy synchronized with sg.data[] whenever entries are transferred, shifted, split, or copied into a new sk_msg. Clear the bit when an entry is replaced by a newly allocated private page or freed. This covers the BPF pull/push/pop helpers, sk_msg_shift_left/right(), sk_msg_xfer(), and tls_split_open_record(), including the partial tail entry created during TLS open-record splitting.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-63830
EUVD
EUVD-2026-45496

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of the sk_msg sg.copy bitmap during scatterlist (SG) transforms. The sg.copy bitmap tracks ownership of scatterlist entries to prevent exposing non-private pages to writable BPF context data. When SG transforms move, copy, or modify entries without updating sg.copy, externally backed entries may become writable, allowing BPF stores to modify original page cache data.

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF and networking subsystems. Detection requires checking kernel versions and BPF-related configurations. No direct commands are provided in the context, but monitoring for unusual BPF program behavior or kernel crashes may indicate exploitation.

Impact Analysis

This vulnerability could allow an attacker with BPF capabilities to modify kernel memory, potentially leading to privilege escalation, data corruption, or denial of service. Systems using BPF with network message processing may be at risk if SG transforms are performed without proper sg.copy synchronization.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it pertains to a Linux kernel memory handling issue in BPF (Berkeley Packet Filter) operations. There is no evidence in the provided context that this flaw leads to data breaches or unauthorized access to sensitive information.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves this vulnerability. Monitor kernel security advisories for patches addressing CVE-2026-63830.

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