{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23086","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-01-13T15:37:45.961Z","datePublished":"2026-02-04T16:08:10.047Z","dateUpdated":"2026-05-11T21:59:43.793Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-05-11T21:59:43.793Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvsock/virtio: cap TX credit to local buffer size\n\nThe virtio transports derives its TX credit directly from peer_buf_alloc,\nwhich is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value.\n\nOn the host side this means that the amount of data we are willing to\nqueue for a connection is scaled by a guest-chosen buffer size, rather\nthan the host's own vsock configuration. A malicious guest can advertise\na large buffer and read slowly, causing the host to allocate a\ncorrespondingly large amount of sk_buff memory.\nThe same thing would happen in the guest with a malicious host, since\nvirtio transports share the same code base.\n\nIntroduce a small helper, virtio_transport_tx_buf_size(), that\nreturns min(peer_buf_alloc, buf_alloc), and use it wherever we consume\npeer_buf_alloc.\n\nThis ensures the effective TX window is bounded by both the peer's\nadvertised buffer and our own buf_alloc (already clamped to\nbuffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer\ncannot force the other to queue more data than allowed by its own\nvsock settings.\n\nOn an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with\n32 guest vsock connections advertising 2 GiB each and reading slowly\ndrove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only\nrecovered after killing the QEMU process. That said, if QEMU memory is\nlimited with cgroups, the maximum memory used will be limited.\n\nWith this patch applied:\n\n  Before:\n    MemFree:        ~61.6 GiB\n    Slab:           ~142 MiB\n    SUnreclaim:     ~117 MiB\n\n  After 32 high-credit connections:\n    MemFree:        ~61.5 GiB\n    Slab:           ~178 MiB\n    SUnreclaim:     ~152 MiB\n\nOnly ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest\nremains responsive.\n\nCompatibility with non-virtio transports:\n\n  - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per\n    socket based on the local vsk->buffer_* values; the remote side\n    cannot enlarge those queues beyond what the local endpoint\n    configured.\n\n  - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and\n    an MTU bound; there is no peer-controlled credit field comparable\n    to peer_buf_alloc, and the remote endpoint cannot drive in-flight\n    kernel memory above those ring sizes.\n\n  - The loopback path reuses virtio_transport_common.c, so it\n    naturally follows the same semantics as the virtio transport.\n\nThis change is limited to virtio_transport_common.c and thus affects\nvirtio-vsock, vhost-vsock, and loopback, bringing them in line with the\n\"remote window intersected with local policy\" behaviour that VMCI and\nHyper-V already effectively have.\n\n[Stefano: small adjustments after changing the previous patch]\n[Stefano: tweak the commit message]"}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/vmw_vsock/virtio_transport_common.c"],"versions":[{"version":"06a8fc78367d070720af960dcecec917d3ae5f3b","lessThan":"fef7110ae5617555c792a2bb4d27878d84583adf","status":"affected","versionType":"git"},{"version":"06a8fc78367d070720af960dcecec917d3ae5f3b","lessThan":"d9d5f222558b42f6277eafaaa6080966faf37676","status":"affected","versionType":"git"},{"version":"06a8fc78367d070720af960dcecec917d3ae5f3b","lessThan":"c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce","status":"affected","versionType":"git"},{"version":"06a8fc78367d070720af960dcecec917d3ae5f3b","lessThan":"84ef86aa7120449828d1e0ce438c499014839711","status":"affected","versionType":"git"},{"version":"06a8fc78367d070720af960dcecec917d3ae5f3b","lessThan":"8ee784fdf006cbe8739cfa093f54d326cbf54037","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/vmw_vsock/virtio_transport_common.c"],"versions":[{"version":"4.8","status":"affected"},{"version":"0","lessThan":"4.8","status":"unaffected","versionType":"semver"},{"version":"6.1.162","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.122","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.68","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.8","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"6.19","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.1.162"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.6.122"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.12.68"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.18.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.8","versionEndExcluding":"6.19"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/fef7110ae5617555c792a2bb4d27878d84583adf"},{"url":"https://git.kernel.org/stable/c/d9d5f222558b42f6277eafaaa6080966faf37676"},{"url":"https://git.kernel.org/stable/c/c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce"},{"url":"https://git.kernel.org/stable/c/84ef86aa7120449828d1e0ce438c499014839711"},{"url":"https://git.kernel.org/stable/c/8ee784fdf006cbe8739cfa093f54d326cbf54037"}],"title":"vsock/virtio: cap TX credit to local buffer size","x_generator":{"engine":"bippy-1.2.0"}}}}