# CVE-2026-3663: xlnt-community xlnt XLSX File compound_document.cpp xsgetn out-of-bounds

> A local attacker can trigger an out-of-bounds read in the xlnt library via a crafted XLSX file, potentially causing crashes or data exposure.

- **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-6v7x-r5hj-8xc6

## What is CVE-2026-3663?

CVE-2026-3663 is a medium-severity memory corruption 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 found in xlnt-community xlnt up to 1.6.1. This issue affects the function xlnt::detail::compound_document_istreambuf::xsgetn of the file source/detail/cryptography/compound_document.cpp of the component XLSX File Parser. Performing a manipulation results in out-of-bounds read. The attack is only possible with local access. The exploit has been made public and could be used. The patch is named 147. It is recommended to apply a patch to fix this issue.

Weakness: CWE-125 (Out-of-bounds Read), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-3663?

It affects 1 product.


Products: Xlnt-Community Xlnt.

## How do I fix CVE-2026-3663?

No fix has been published for CVE-2026-3663 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3663 being exploited?

There is no known exploitation of CVE-2026-3663 in the wild and no public exploit code.

## Other vulnerabilities in xlnt-community xlnt

- [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-2026-3665](https://insights.sbomify.com/CVE-2026-3665/): xlnt-community xlnt XLSX File xlsx_consumer.cpp read_office_document null pointer dereference (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-2026-3663 and fix it if it is affected.

What it is: CVE-2026-3663 is a medium-severity memory corruption 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-2026-3663 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-2026-3663/ (Markdown: https://insights.sbomify.com/CVE-2026-3663/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3663
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3663
- OSV: https://osv.dev/vulnerability/CVE-2026-3663

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-3663/
Summaries are generated and may contain mistakes; the official description above is the record.