CVE-2026-63970

A flaw was found in the Linux kernel's vsock/virtio transport. This vulnerability occurs when the system processes zerocopy socket buffers (skbs) and encounters an error during memory allocation for fixed-buffer vectored data. The system may attempt to free memory incorrectly, leading to a use-after-free condition or memory corruption. This can potentially allow a local attacker to cause a denial of service or escalate their privileges on the system.

A use-after-free memory flaw in the Linux kernel's vsock/virtio transport, rated Important by Red Hat Product Security, affects the kernel packages of Red Hat Enterprise Linux 9 and 10 (kernel and kernel-rt) and Red Hat In-Vehicle OS 2. When a local user sends fixed-buffer vectored data over a virtio vsock socket using zerocopy and the number of fragments reaches MAX_SKB_FRAGS, io_sg_from_iter() may partially attach managed frags and return -EMSGSIZE. The error rollback path then calls kfree_skb() on a socket buffer that carries SKBFL_MANAGED_FRAG_REFS but no zerocopy uarg, so skb_release_data() falls through to an ordinary frag unref, producing a use-after-free or memory corruption. A local attacker able to establish a vsock connection could use this flaw to crash the system (denial of service) or potentially escalate privileges. Red Hat Enterprise Linux 6, 7, 8, and the RHEL 9.2 streams are not affected because the vulnerable code is not present in those versions. A fix is being pursued by the Red Hat kernel team for the affected streams. Red Hat scores this flaw CVSS 7.0 (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H), slightly lower than the upstream CVEORG score of 7.8 (AV:L/AC:L/...), reflecting the higher attack complexity of triggering and reliably exploiting the flawed zerocopy error path.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.