CVE-2026-63830 net: skmsg: preserve sg.copy across SG transforms
A flaw in Linux kernel skmsg handling allows BPF programs to modify page cache, potentially leading to privilege escalation or data corruption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63830?
CVE-2026-63830 is a critical vulnerability in Linux kernel, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-63830?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63830?
Apply the vendor's patch.
Is CVE-2026-63830 being exploited?
There is no known exploitation of CVE-2026-63830 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63830, DEBIAN-CVE-2026-63830, GHSA-82mh-rf6q-rhp7, ROOT-OS-DEBIAN-11-CVE-2026-63830, ROOT-OS-UBUNTU-2204-CVE-2026-63830, UBUNTU-CVE-2026-63830.