# CVE-2026-3665: xlnt-community xlnt XLSX File xlsx_consumer.cpp read_office_document null pointer dereference

> A local attacker can cause a denial of service via null pointer dereference in the xlnt library's XLSX parser.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **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:** No
- **Published:** 7 Mar 2026
- **Updated:** 11 Mar 2026
- **Also known as:** GHSA-f8w4-fphr-9q3w

## What is CVE-2026-3665?

CVE-2026-3665 is a medium-severity vulnerability in xlnt-community xlnt, published on 7 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability was identified in xlnt-community xlnt up to 1.6.1. The affected element is the function xlnt::detail::xlsx_consumer::read_office_document of the file source/detail/serialization/xlsx_consumer.cpp of the component XLSX File Parser. The manipulation leads to null pointer dereference. The attack must be carried out locally. The exploit is publicly available and might be used.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2026-3665?

It affects 1 product.


Products: Xlnt-Community Xlnt.

## How do I fix CVE-2026-3665?

No fix has been published for CVE-2026-3665 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3665 being exploited?

There is no known exploitation of CVE-2026-3665 in the wild and no public exploit code.

## Other vulnerabilities in xlnt-community xlnt

- [CVE-2026-3663](https://insights.sbomify.com/CVE-2026-3663/): xlnt-community xlnt XLSX File compound_document.cpp xsgetn out-of-bounds (medium 4.8)
- [CVE-2026-3664](https://insights.sbomify.com/CVE-2026-3664/): xlnt-community xlnt Encrypted XLSX File compound_document.cpp read_directory out-of-bounds (medium 4.8)
- [CVE-2026-3463](https://insights.sbomify.com/CVE-2026-3463/): xlnt-community xlnt Compound Document binary.hpp append heap-based overflow (medium 4.8)
- [CVE-2026-2703](https://insights.sbomify.com/CVE-2026-2703/): xlnt-community xlnt Encrypted XLSX File base64.cpp decode_base64 off-by-one (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3665 and fix it if it is affected.

What it is: CVE-2026-3665 is a medium-severity vulnerability in xlnt-community xlnt, published on 7 Mar 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-2026-3665 in the wild and no public exploit code.

Affected product: xlnt-community xlnt. 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-2026-3665/ (Markdown: https://insights.sbomify.com/CVE-2026-3665/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3665
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3665
- OSV: https://osv.dev/vulnerability/CVE-2026-3665

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3665/
Summaries are generated and may contain mistakes; the official description above is the record.