# CVE-2026-90183: blk-iolatency: clear delay state when freeing policy data

> A Linux kernel bug in blk-iolatency causes persistent congestion states, leading to severe performance degradation and denial of service for affected cgroups.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102494, BELL-CVE-2026-90183, DEBIAN-CVE-2026-90183, GHSA-62h3-pvxj-c2v2, UBUNTU-CVE-2026-90183

## What is CVE-2026-90183?

CVE-2026-90183 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-iolatency: clear delay state when freeing policy data

io.latency can throttle a group which has no latency target of its own.
When a sibling misses its target, check_scale_change() scales down its
peers, and a peer that reaches queue depth one gets blkcg_use_delay()
called on it on every further scale-down, even with min_lat_nsec == 0.

iolatency_pd_offline() resets the target through
iolatency_set_min_lat_nsec(), which clears the delay only on a nonzero
to zero transition, so it never clears such a peer.  Freeing the policy
data then leaves blkg->use_delay set and blkcg->congestion_count
elevated with nothing left that can drop it.

blk_cgroup_congested() then returns true for every task in that cgroup
and its descendants for as long as the cgroup lives: 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 the delay in iolatency_pd_free().  By then bio-held blkg
references have drained, or the queue is frozen for policy
deactivation, so check_scale_change() cannot 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-2026-90183?


## How do I fix CVE-2026-90183?

Apply the vendor's patch.

## Is CVE-2026-90183 being exploited?

There is no known exploitation of CVE-2026-90183 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90183 and fix it if it is affected.

What it is: CVE-2026-90183 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.
Exploitation: There is no known exploitation of CVE-2026-90183 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-90183/ (Markdown: https://insights.sbomify.com/CVE-2026-90183/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90183
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90183
- OSV: https://osv.dev/vulnerability/CVE-2026-90183

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90183/
Summaries are generated and may contain mistakes; the official description above is the record.