vsock/virtio: cap TX credit to local buffer size
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: M
CVE-2026-23086
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-23086
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "06a8fc78367d070720af960dcecec917d3ae5f3b",
"lessThan": "fef7110ae5617555c792a2bb4d27878d84583adf",
"versionType": "git"
},
{
"status": "affected",
"version": "06a8fc78367d070720af960dcecec917d3ae5f3b",
"lessThan": "d9d5f222558b42f6277eafaaa6080966faf37676",
"versionType": "git"
},
{
"status": "affected",
"version": "06a8fc78367d070720af960dcecec917d3ae5f3b",
"lessThan": "c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce",
"versionType": "git"
},
{
"status": "affected",
"version": "06a8fc78367d070720af960dcecec917d3ae5f3b",
"lessThan": "84ef86aa7120449828d1e0ce438c499014839711",
"versionType": "git"
},
{
"status": "affected",
"version": "06a8fc78367d070720af960dcecec917d3ae5f3b",
"lessThan": "8ee784fdf006cbe8739cfa093f54d326cbf54037",
"versionType": "git"
}
],
"programFiles": [
"net/vmw_vsock/virtio_transport_common.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.1.162",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.122",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.68",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.8",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/vmw_vsock/virtio_transport_common.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-23086
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #39746 · Revision 1
- Added to Heist Feed
- Publisher date