# CVE-2026-45892: ext4: drop extent cache after doing PARTIAL_VALID1 zeroout

> A logic error in the Linux kernel ext4 filesystem can leave stale extent cache entries, potentially leading to data corruption or incorrect data reads during specific write operations.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 27 May 2026
- **Updated:** 30 May 2026
- **Also known as:** AZL-88581, BELL-CVE-2026-45892, DEBIAN-CVE-2026-45892, GHSA-xq2x-f6m4-2hrp, ROOT-OS-DEBIAN-11-CVE-2026-45892, ROOT-OS-DEBIAN-12-CVE-2026-45892, ROOT-OS-UBUNTU-2204-CVE-2026-45892, ROOT-OS-UBUNTU-2404-CVE-2026-45892, UBUNTU-CVE-2026-45892

## What is CVE-2026-45892?

CVE-2026-45892 is a medium-severity vulnerability in Linux kernel, published on 27 May 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:

ext4: drop extent cache after doing PARTIAL_VALID1 zeroout

When splitting an unwritten extent in the middle and converting it to
initialized in ext4_split_extent() with the EXT4_EXT_MAY_ZEROOUT and
EXT4_EXT_DATA_VALID2 flags set, it could leave a stale unwritten extent.

Assume we have an unwritten file and buffered write in the middle of it
without dioread_nolock enabled, it will allocate blocks as written
extent.

       0  A      B  N
       [UUUUUUUUUUUU] on-disk extent      U: unwritten extent
       [UUUUUUUUUUUU] extent status tree
       [--DDDDDDDD--]                     D: valid data
          |<-  ->| ----> this range needs to be initialized

ext4_split_extent() first try to split this extent at B with
EXT4_EXT_DATA_PARTIAL_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but
ext4_split_extent_at() failed to split this extent due to temporary lack
of space. It zeroout B to N and leave the entire extent as unwritten.

       0  A      B  N
       [UUUUUUUUUUUU] on-disk extent
       [UUUUUUUUUUUU] extent status tree
       [--DDDDDDDDZZ]                     Z: zeroed data

ext4_split_extent() then try to split this extent at A with
EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and
leave an written extent from A to N.

       0  A      B  N
       [UUWWWWWWWWWW] on-disk extent      W: written extent
       [UUUUUUUUUUUU] extent status tree
       [--DDDDDDDDZZ]

Finally ext4_map_create_blocks() only insert extent A to B to the extent
status tree, and leave an stale unwritten extent in the status tree.

       0  A      B  N
       [UUWWWWWWWWWW] on-disk extent      W: written extent
       [UUWWWWWWWWUU] extent status tree
       [--DDDDDDDDZZ]

Fix this issue by always cached extent status entry after zeroing out
the second part.

## Which versions are affected by CVE-2026-45892?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45892?

Apply the vendor's patch.

## Is CVE-2026-45892 being exploited?

There is no known exploitation of CVE-2026-45892 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45892 and fix it if it is affected.

What it is: CVE-2026-45892 is a medium-severity vulnerability in Linux kernel, published on 27 May 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-2026-45892 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-45892/ (Markdown: https://insights.sbomify.com/CVE-2026-45892/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45892
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45892
- OSV: https://osv.dev/vulnerability/CVE-2026-45892

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45892/
Summaries are generated and may contain mistakes; the official description above is the record.