Executive brief
A vulnerability exists in the Linux kernel's virtio_net driver, which is commonly used for networking in virtualized environments. Under specific network configurations, the system may attempt to access memory that has already been freed when a network namespace is deleted. This can lead to a system crash (kernel panic), potentially disrupting services or allowing an attacker with local access to compromise the system's stability.
Technical details
A use-after-free (UAF) vulnerability exists in the virtio_net driver when configured with napi_tx=N and the IFF_XMIT_DST_RELEASE flag is cleared. When the flag is cleared, the network stack expects the driver to hold the skb->dst reference until transmission is complete. If the network namespace is destroyed while packets are still pending in the transmit ring, the associated dst_ops structure is freed. A subsequent transmission triggers free_old_xmit(), which calls dst_release() on the stale entry, resulting in a kernel paging request failure. The fix involves adding skb_dst_drop(skb) in the start_xmit function to release the reference before the skb is queued.
Affected products
- Linux Linux Kernel 7.0.0-rc1+
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
Timeline
- 2026-03-12: other: Patch authored
- 2026-04-22: advisory: CVE published
References
- https://git.kernel.org/stable/c/63d45077b97bb0e0fe0c75931acbbca7a47af141
- https://git.kernel.org/stable/c/8a4790850e710fd6771e4d2112168ed1dd6c0e54
- https://git.kernel.org/stable/c/9a18629f2525781f0f3dda7be72b204e4cf77d08
- https://git.kernel.org/stable/c/ba8bda9a0896746053aa97ac6c3e08168729172c
- https://git.kernel.org/stable/c/be0e63f3b97bbaf453c542e8a15ba2a536e2ac01
- https://git.kernel.org/stable/c/c1ec36cb3768574b916f20d2d7415fd14fa1bf12
- https://git.kernel.org/stable/c/f04733c4dc40c43899c3d1c97afbae5831a3770f