# CVE-2026-90043: zram: fix slot lock bit position on big-endian 64-bit

> A race condition in the Linux kernel zram driver on big-endian systems allows concurrent slot access, potentially causing denial of service or data corruption.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-90043, GHSA-6w7g-56x2-f4jj, UBUNTU-CVE-2026-90043

## What is CVE-2026-90043?

CVE-2026-90043 is a high-severity vulnerability in Linux, published on 16 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:

zram: fix slot lock bit position on big-endian 64-bit

The slot lock is a bit operation on the whole __lock word, which flags and
ac_time alias as two u32s.  On little-endian the lock bit lands in the
position ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out.  On
64-bit big-endian it lands in ac_time instead: with
ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from
mark_slot_accessed() or slot_free() wipes out the held lock bit, letting
another CPU take the same slot lock; an access time value with that bit
set makes the slot look locked forever.

Shift the lock bit into the flags half of the word on big-endian 64-bit.

## Which versions are affected by CVE-2026-90043?


## How do I fix CVE-2026-90043?

Apply the vendor's patch.

## Is CVE-2026-90043 being exploited?

There is no known exploitation of CVE-2026-90043 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90043 and fix it if it is affected.

What it is: CVE-2026-90043 is a high-severity vulnerability in Linux, published on 16 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-2026-90043 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-2026-90043/ (Markdown: https://insights.sbomify.com/CVE-2026-90043/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90043
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90043
- OSV: https://osv.dev/vulnerability/CVE-2026-90043

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90043/
Summaries are generated and may contain mistakes; the official description above is the record.