CVE-2026-23069: vsock/virtio: fix potential underflow in virtio_transport_get_credit()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-04 · updated 2026-10-19
Weakness: CWE-191

Description

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix potential underflow in virtio_transport_get_credit() The credit calculation in virtio_transport_get_credit() uses unsigned arithmetic: ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt); If the peer shrinks its advertised buffer (peer_buf_alloc) while bytes are in flight, the subtraction can underflow and produce a large positive value, potentially allowing more data to be queued than the peer can handle. Reuse virtio_transport_has_space() which already handles this case and add a comment to make it clear why we are doing that. [Stefano: use virtio_transport_has_space() instead of duplicating the code] [Stefano: tweak the commit message]

Affected products

Linux kernel: from 4.8 before 6.1.162; from 6.2 before 6.6.122; from 6.7 before 6.12.68; from 6.13 before 6.18.8; 6.19-rc1, 6.19-rc2, 6.19-rc3, 6.19-rc4, 6.19-rc5, 6.19-rc6 — fixed in 6.1.162, 6.12.68, 6.18.8, 6.6.122

How to fix

Upgrade to a fixed version: Linux kernel 6.1.162, 6.12.68, 6.18.8, 6.6.122. Check the vendor advisory for mitigations.

References

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