CVE-2026-63830: 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 p...

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.

Metrics

CVSS 3.1

9.4/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

EPSS Probability

0.35%

27.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < f126eed589eec6f201405abbc398844042ef6d57; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 31a110642b5fb5e61940cbcfb503445ac4f28017; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 9bb86d8184b37503816150c4a6ad3c17dfdbe827; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 0eb4c16c4adb262763bda870a8ed38a1a9dec7ec; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < d22cc92bc41290e5783a72375e0843d9435f6001; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 1acdd14c0990dd1cd4b6534f00366d2e6dfce05f; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 21ed9540a8e1906dfcbc1bb82ba9b4de4fa4bd6d; >= d3b18ad31f93d0b6bae105c679018a1ba7daa9ca, < 406e8a651a7b854c41fecd5117bb282b3a6c2c6b
Linux	Linux	4.20

References

Timeline

Published: Jul 19, 2026
Last Modified: Jul 27, 2026
Status: Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63830?

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.

How severe is CVE-2026-63830?

CVE-2026-63830 has a CVSS score of 9.4/10 (CRITICAL severity). The EPSS model estimates a 0.35% probability of exploitation in the next 30 days.

How do I fix CVE-2026-63830?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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