CVE-2026-63830
CriticalCVSS 9.4Exploitation Probability (EPSS)
Low risk28th percentile - higher than 28% of all known CVEs
Summary
In the Linux kernel, a vulnerability in the sk_msg mechanism where the sg.copy bit is not properly synchronized during scatterlist transforms. This can expose file page-cache pages as writable by BPF, allowing modification of the original page cache.
Risk Assessment
Risk of file page-cache data modification by unauthorized BPF programs, potentially leading to data integrity issues and privilege escalation.
Recommendation
Update the Linux kernel to a patched version and restrict BPF program access to trusted entities only.
Original NVD description (English source)
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.