# CVE-2026-53165: iomap: avoid potential null folio->mapping deref during error reporting

> A race condition in the Linux kernel iomap subsystem can cause a null pointer dereference during error reporting, leading to a system crash.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-53165, GHSA-f5cm-4mmf-92c9, ROOT-OS-UBUNTU-2204-CVE-2026-53165, ROOT-OS-UBUNTU-2404-CVE-2026-53165, UBUNTU-CVE-2026-53165

## What is CVE-2026-53165?

CVE-2026-53165 is a high-severity vulnerability in Linux kernel, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

iomap: avoid potential null folio->mapping deref during error reporting

When a buffered read fails, iomap_finish_folio_read() reports the error
with fserror_report_io(folio->mapping->host, ...). This is called after
ifs->read_bytes_pending has been decremented by the bytes attempted to
be read.

For a folio split across multiple read completions, the folio is only
guaranteed to stay locked while read_bytes_pending > 0. Once
iomap_finish_folio_read() decrements read_bytes_pending, another
in-flight read can complete and end the read on the folio, which unlocks
it. This allows truncate logic to run and detach the folio (set
folio->mapping to NULL). The error reporting path then can dereference a
NULL folio->mapping. As reported by Sam Sun, this is the race that can
occur:

CPU0: failed completion      CPU1: final completion     CPU2: truncate
-----------------------      ----------------------     --------------
read_bytes_pending -= len
finished = false
/* preempted before
   fserror_report_io() */
			     read_bytes_pending -= len
			     finished = true
			     folio_end_read()
							truncate clears
							folio->mapping
fserror_report_io(
  folio->mapping->host, ...)
	      ^ NULL deref

Fix this by reporting the error first before decrementing
ifs->read_bytes_pending.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-53165?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53165?

Apply the vendor's patch.

## Is CVE-2026-53165 being exploited?

There is no known exploitation of CVE-2026-53165 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-2026-53165 and fix it if it is affected.

What it is: CVE-2026-53165 is a high-severity vulnerability in Linux kernel, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53165 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-2026-53165/ (Markdown: https://insights.sbomify.com/CVE-2026-53165/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53165
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53165
- OSV: https://osv.dev/vulnerability/CVE-2026-53165

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53165/
Summaries are generated and may contain mistakes; the official description above is the record.