# CVE-2026-3463: xlnt-community xlnt Compound Document binary.hpp append heap-based overflow

> A heap-based buffer overflow in the xlnt library's Compound Document parser allows local attackers to execute arbitrary code or cause denial of service.

- **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:** 3 Mar 2026
- **Updated:** 3 Mar 2026
- **Also known as:** GHSA-hhjx-x77r-qp36

## What is CVE-2026-3463?

CVE-2026-3463 is a medium-severity memory corruption vulnerability in xlnt-community xlnt, published on 3 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A weakness has been identified in xlnt-community xlnt up to 1.6.1. Impacted is the function xlnt::detail::binary_writer::append of the file source/detail/binary.hpp of the component Compound Document Parser. This manipulation causes heap-based buffer overflow. The attack can only be executed locally. The exploit has been made available to the public and could be used for attacks. Patch name: 147. It is suggested to install a patch to address this issue.

Weakness: CWE-122 (Heap-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-3463?

It affects 1 product.


Products: Xlnt-Community Xlnt.

## How do I fix CVE-2026-3463?

No fix has been published for CVE-2026-3463 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3463 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3463 exists.

## 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-2026-3665](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-2026-2703](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-2026-3463 and fix it if it is affected.

What it is: CVE-2026-3463 is a medium-severity memory corruption vulnerability in xlnt-community xlnt, published on 3 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3463 exists.

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-2026-3463/ (Markdown: https://insights.sbomify.com/CVE-2026-3463/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3463
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3463
- OSV: https://osv.dev/vulnerability/CVE-2026-3463

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-3463/
Summaries are generated and may contain mistakes; the official description above is the record.