critical CVSS 9.8

CVE-2026-99079·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Prevent stale XSK buffer release on refill retry When an XDP redirect to an AF_XDP socket fails because its RX ring is full, the XSK core frees the buffer. During the subsequent batched refill of a legacy cyclic RQ, mlx5e also releases the WQE's XSK buffer before allocating a replacement. If that refill succeeds only partially, a WQE left without a replacement retains its old buffer pointer. The buffer can meanwhile be allocated to another WQE. A later refill retry can then free the live buffer through the stale pointer and publish the same UMEM frame twice. Mark the WQE as released immediately after the driver-side free. The flag is already cleared when a replacement buffer is assigned, so refill retries no longer release stale pointers. The failure is silent and produces no kernel warning or splat. A standalone legacy cyclic-RQ zero-copy libxsk reproducer, using 64-byte UDP traffic offered at 12 Mpps, detected it: stock stopped after 2,854,914 packets in 4.094 seconds, with 4,542 xdp_rx_ring_full events and 64 ownership/double-publication errors. With this change it processed 356,904,225 packets in 30 seconds despite 571,405 xdp_rx_ring_full events, with no ownership or data errors.

Severity
critical
Software
Kernel
Fixed in
6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3
Published

How to fix this CVE

CVE-2026-99079 is a critical kernel vulnerability affecting XDP/AF_XDP socket buffer management that can cause memory corruption and double-publication of UMEM frames. Update your kernel to one of the patched stable releases: 6.6.160, 6.12.113, 6.18.57, 7.2.11, or mainline 7.3 and later. Install your distribution's patched kernel package rather than jumping to mainline unless you are already running a newer kernel line.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your kernel version: uname -r
  2. Compare against fixed versions: 6.6.160+, 6.12.113+, 6.18.57+, 7.2.11+, or 7.3+
  3. Verify if XDP and AF_XDP are in use: grep -i xdp /proc/cmdline or ethtool -i <interface> | grep -i xdp
  4. After patching, reboot and confirm new kernel: uname -r and verify version matches a patched release

FAQ

What is CVE-2026-99079?

This vulnerability occurs in the Linux kernel's mlx5e driver when XDP redirect to an AF_XDP socket fails due to a full RX ring. The driver may release and reuse XSK buffers incorrectly, causing the same memory frame to be published twice and corrupting zero-copy packet processing.

Is CVE-2026-99079 being actively exploited?

No, there is no evidence of active exploitation in the wild. This is a logical flaw in buffer management that manifests as silent memory corruption rather than a direct attack vector.

What versions of Kernel are affected by CVE-2026-99079?

All kernel versions before the stable fixes are affected. Patched versions are 6.6.160, 6.12.113, 6.18.57, 7.2.11, and mainline 7.3 and later.

How do I check if my server is vulnerable to CVE-2026-99079?

Run 'uname -r' and compare your kernel version to the fixed versions. If your kernel is older than 6.6.160, 6.12.113, 6.18.57, 7.2.11, or 7.3, you are vulnerable only if you are using XDP with AF_XDP sockets.

Does Defensia detect CVE-2026-99079?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2026-99079 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-63795CVSS 10In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error path When p9_client_walk() is called with clone set to false, fid aliases oldfid. If the walk subsequently fails after the request has been sent, the error path jumps to clunk_fid, which currently calls p9_fid_put(fid) unconditionally. This drops a reference to oldfid even though ownership of oldfid remains with the caller. If this is the last reference, oldfid can be clunked and destroyed while the caller still expects it to be valid. A later use or put of oldfid can then trigger a use-after-free or refcount underflow. Fix this by only putting fid in the clunk_fid error path when it does not alias oldfid, matching the existing guard in the error path below. This can be triggered when a multi-component walk is split into multiple p9_client_walk() calls and a later non-cloning walk fails. A reproducer and refcount warning logs are available on request.
CVE-2026-64160CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix potential for tearing in ->remote_i_size and ->zero_point Fix potential tearing in using ->remote_i_size and ->zero_point by copying i_size_read() and i_size_write() and using the same seqcount as for i_size. We need to make sure that netfslib and the filesystems that use it always hold i_lock whilst updating any of the sizes to prevent i_size_seqcount from getting corrupted.
CVE-2026-64125CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: bcmgenet: keep RBUF EEE/PM disabled Setting RBUF_EEE_EN | RBUF_PM_EN in RBUF_ENERGY_CTRL breaks the RX path on GENET hardware once MAC EEE becomes active. RX traffic stops flowing while the link stays up and the usual descriptor/RX error counters remain quiet. In that state the MAC still accepts frames (rbuf_ovflow_cnt keeps climbing) but RBUF no longer forwards them to DMA, so rx_packets is no longer incremented at the netdev level. On some boards the corruption ends up as a paging fault in skb_release_data via bcmgenet_rx_poll on an LPI exit. Reproduced on Pi 4B (BCM2711 + BCM54213PE) and confirmed by Florian Fainelli on an internal Broadcom 4908-family board with the same crash signature. RBUF_PM_EN is not publicly documented. This shows up more often now that phy_support_eee() enables EEE by default, but it also affects older kernels as soon as TX LPI is turned on via ethtool, so it is not specific to recent changes. Always clear RBUF_EEE_EN | RBUF_PM_EN in bcmgenet_eee_enable_set so the bits stay off across resets. UMAC and TBUF setup is left alone so TX-side EEE keeps working.
CVE-2026-64136CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked() Commit 96c4af418586 ("cifs: Fix locking usage for tcon fields") refactored cifs code to change cifs_tcp_ses_lock for tc_lock around tc_count changes. There was missing lock around tc_count increment inside smb2_find_smb_sess_tcon_unlocked().
CVE-2026-53399CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nfsd: release layout stid on setlease failure nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer. The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail. A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work. nfsd4_alloc_layout_stateid() nfs4_alloc_stid() /* idr_alloc_cyclic under cl_lock */ nfsd4_layout_setlease() /* fails */ nfs4_put_stid() nfsd4_free_layout_stateid() delayed_work_pending(&ls->ls_fence_work) /* needs INIT */ nfsd4_close_layout() /* nfsd_file_put(ls->ls_file) */ put_nfs4_file() Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).

References

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