cbcvebase.
CVE-2026-23086
published 2026-02-04

CVE-2026-23086: In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: cap TX credit to local buffer size The virtio transports derives its TX…

PriorityP423medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.14%
4.0th percentile
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: cap TX credit to local buffer size The virtio transports derives its TX credit directly from peer_buf_alloc, which is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value. On the host side this means that the amount of data we are willing to queue for a connection is scaled by a guest-chosen buffer size, rather than the host's own vsock configuration. A malicious guest can advertise a large buffer and read slowly, causing the host to allocate a correspondingly large amount of sk_buff memory. The same thing would happen in the guest with a malicious host, since virtio transports share the same code base. Introduce a small helper, virtio_transport_tx_buf_size(), that returns min(peer_buf_alloc, buf_alloc), and use it wherever we consume peer_buf_alloc. This ensures the effective TX window is bounded by both the peer's advertised buffer and our own buf_alloc (already clamped to buffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer cannot force the other to queue more data than allowed by its own vsock settings. On an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with 32 guest vsock connections advertising 2 GiB each and reading slowly drove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only recovered after killing the QEMU process. That said, if QEMU memory is limited with cgroups, the maximum memory used will be limited. With this patch applied: Before: MemFree: ~61.6 GiB Slab: ~142 MiB SUnreclaim: ~117 MiB After 32 high-credit connections: MemFree: ~61.5 GiB Slab: ~178 MiB SUnreclaim: ~152 MiB Only ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest remains responsive. Compatibility with non-virtio transports: - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per socket based on the local vsk->buffer_* values; the remote side cannot enlarge those queues beyond what the local endpoint configured. - Hyper-V's

Affected

53 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
debianlinux-6.1< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
linuxlinux
linuxlinux>= 06a8fc78367d070720af960dcecec917d3ae5f3b < fef7110ae5617555c792a2bb4d27878d84583adffef7110ae5617555c792a2bb4d27878d84583adf
linuxlinux>= 06a8fc78367d070720af960dcecec917d3ae5f3b < d9d5f222558b42f6277eafaaa6080966faf37676d9d5f222558b42f6277eafaaa6080966faf37676
linuxlinux>= 06a8fc78367d070720af960dcecec917d3ae5f3b < c0e42fb0e054c2b2ec4ee80f48ccd256ae0227cec0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce
linuxlinux>= 06a8fc78367d070720af960dcecec917d3ae5f3b < 84ef86aa7120449828d1e0ce438c49901483971184ef86aa7120449828d1e0ce438c499014839711
linuxlinux>= 06a8fc78367d070720af960dcecec917d3ae5f3b < 8ee784fdf006cbe8739cfa093f54d326cbf540378ee784fdf006cbe8739cfa093f54d326cbf54037
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 0 < 6.1.162-16.1.162-1
linuxlinux_kernel>= 0 < 6.12.69-16.12.69-1
linuxlinux_kernel>= 0 < 6.18.8-16.18.8-1
linuxlinux_kernel>= 4.8 < 6.1.1626.1.162
linuxlinux_kernel>= 6.13 < 6.18.86.18.8
linuxlinux_kernel>= 6.2 < 6.6.1226.6.122
linuxlinux_kernel>= 6.7 < 6.12.686.12.68
msrccbl2_kernel_5.15.200.1-1_on_cbl_mariner_2.0
msrccbl2_kernel_5.15.202.1-1_on_cbl_mariner_2.0
ubuntulinux
ubuntulinux-aws

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
vendor_ubuntu7.8HIGH
vendor_debian5.5MEDIUM
vendor_msrc5.5MEDIUM
vendor_redhat5.5MEDIUM
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