# CVE-2025-68794: iomap: adjust read range correctly for non-block-aligned positions

> An integer underflow in the Linux kernel iomap subsystem can cause incorrect read ranges, potentially leading to a denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 13 Jan 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-74483, BELL-CVE-2025-68794, DEBIAN-CVE-2025-68794, GHSA-3c24-c79w-qw24, ROOT-OS-DEBIAN-11-CVE-2025-68794, ROOT-OS-DEBIAN-12-CVE-2025-68794, ROOT-OS-UBUNTU-2204-CVE-2025-68794, ROOT-OS-UBUNTU-2404-CVE-2025-68794, UBUNTU-CVE-2025-68794

## What is CVE-2025-68794?

CVE-2025-68794 is a critical vulnerability in Linux, published on 13 Jan 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: adjust read range correctly for non-block-aligned positions

iomap_adjust_read_range() assumes that the position and length passed in
are block-aligned. This is not always the case however, as shown in the
syzbot generated case for erofs. This causes too many bytes to be
skipped for uptodate blocks, which results in returning the incorrect
position and length to read in. If all the blocks are uptodate, this
underflows length and returns a position beyond the folio.

Fix the calculation to also take into account the block offset when
calculating how many bytes can be skipped for uptodate blocks.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2025-68794?


## How do I fix CVE-2025-68794?

Apply the vendor's patch.

## Is CVE-2025-68794 being exploited?

There is no known exploitation of CVE-2025-68794 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68794 and fix it if it is affected.

What it is: CVE-2025-68794 is a critical vulnerability in Linux, published on 13 Jan 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-2025-68794 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-2025-68794/ (Markdown: https://insights.sbomify.com/CVE-2025-68794/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68794
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68794
- OSV: https://osv.dev/vulnerability/CVE-2025-68794

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68794/
Summaries are generated and may contain mistakes; the official description above is the record.