CVE-2026-90182 blk-iocost: clear delay state when freeing policy data
A local attacker can cause persistent I/O throttling and performance degradation in Linux by triggering a state management error in the blk-iocost scheduler.
- 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-2026-90182?
CVE-2026-90182 is a denial of service vulnerability in Linux, published on 17 Sep 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:
blk-iocost: clear delay state when freeing policy data
iocg_kick_delay() turns sufficiently large debt into an explicit block-cgroup delay with blkcg_set_delay(), setting blkg->use_delay to -1 and incrementing blkcg->congestion_count. Clearing it again depends on iocg_kick_delay() running from the period timer, the waitq timer or the issue path.
ioc_pd_free() removes the iocg from active_iocgs and cancels its waitq timer, and no further bios can arrive, so once it has run nothing is left which can reduce the debt and clear the delay. The blkcg stays marked congested for the rest of its life.
blk_cgroup_congested() then returns true for every task in that cgroup and its descendants: page_cache_sync_ra() cuts readahead to a single page, page_cache_async_ra() skips it altogether, and __folio_throttle_swaprate() takes swap_avail_lock and schedules a throttle on anonymous folio allocation.
Clear it explicitly, after the list removal and the synchronous hrtimer_cancel() so that neither timer processing nor an I/O path can re-arm it. The free callback can also see policy data which was never attached to a blkg, hence the pd->blkg check.
Which versions are affected by CVE-2026-90182?
How do I fix CVE-2026-90182?
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-2026-90182 being exploited?
There is no known exploitation of CVE-2026-90182 in the wild and no public exploit code.
Sources
Also known as AZL-101951, BELL-CVE-2026-90182, DEBIAN-CVE-2026-90182, GHSA-3p27-2gjm-jxc2, UBUNTU-CVE-2026-90182.