CVE-2026-98489 net: atl1c: fix soft lockup on out-of-range tpd_cons read
A remote attacker can cause a kernel soft lockup and system hang by triggering a specific hardware state in the atl1c network driver.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98489?
CVE-2026-98489 is a denial of service vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: atl1c: fix soft lockup on out-of-range tpd_cons read
The hardware can report an out-of-range tpd_cons (seen as 0xffff) while the PCIe link/MAC is resetting. An out-of-range value can never be reached and the loop below would spin forever. To avoid a soft lockup treat it as "nothing new to clean" instead.
Reproduced on two machines, same NIC (Qualcomm Atheros AR8151 v2.0, 4-port), triggered by rebooting a Mikrotik CCR2004 PCIe card that the ports are directly linked to:
- Ubuntu 26.04.1 LTS, kernel 7.0.0-31-generic. The link-flap precursor, before the lockup was captured with a full trace elsewhere:
atl1c 0000:05:00.0 enp5s0f0: NETDEV WATCHDOG: CPU: 4: transmit queue 2 timed out 489984 ms atl1c 0000:05:00.0: MAC state machine can't be idle since disabled for 10ms second atl1c 0000:05:00.0: atl1c: enp5s0f0 NIC Link is Up<65535 Mbps Full Duplex>
65535 (0xffff) here is the same value tpd_cons reads back once the loop below gets stuck.
- Proxmox VE, kernel 7.0.14-11-pve. Same NIC/trigger, this time caught by the soft lockup watchdog with a full stack trace:
watchdog: BUG: soft lockup - CPU#12 stuck for 354s! [napi/eth%d-0:329] CPU: 12 UID: 0 PID: 329 Comm: napi/eth%d-0 Tainted: P O L 7.0.14-11-pve #1 PREEMPT(lazy) RIP: 0010:atl1c_clean_tx+0x142/0x2d0 [atl1c] Call Trace: <TASK> __napi_poll+0x32/0x1e0 napi_threaded_poll_loop+0x286/0x2e0 napi_threaded_poll+0xfd/0x140 kthread+0xf7/0x130 ret_from_fork+0x2da/0x3a0 ret_from_fork_asm+0x1a/0x30 </TASK>
Which versions are affected by CVE-2026-98489?
How do I fix CVE-2026-98489?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98489 being exploited?
There is no known exploitation of CVE-2026-98489 in the wild and no public exploit code.
Sources
Also known as AZL-108698, BELL-CVE-2026-98489, DEBIAN-CVE-2026-98489, GHSA-v9fj-6g8j-jj53, UBUNTU-CVE-2026-98489.