# CVE-2026-2703: xlnt-community xlnt Encrypted XLSX File base64.cpp decode_base64 off-by-one

> An off-by-one error in the base64 decoder of the xlnt library allows attackers to cause memory corruption via crafted encrypted XLSX files.

- **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:** 19 Feb 2026
- **Updated:** 24 Feb 2026
- **Also known as:** GHSA-pf2p-f275-6cmx

## What is CVE-2026-2703?

CVE-2026-2703 is a medium-severity vulnerability in xlnt-community xlnt, published on 19 Feb 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::decode_base64 of the file source/detail/cryptography/base64.cpp of the component Encrypted XLSX File Parser. Executing a manipulation can lead to off-by-one. The attack requires local access. The exploit has been made available to the public and could be used for attacks. This patch is called f2d7bf494e5c52706843cf7eb9892821bffb0734. Applying a patch is advised to resolve this issue.

Weakness: CWE-193 (Off-by-one Error), CWE-189

## Which versions are affected by CVE-2026-2703?

It affects 1 product.


Products: Xlnt-Community Xlnt.

## How do I fix CVE-2026-2703?

No fix has been published for CVE-2026-2703 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-2703 being exploited?

There is no known exploitation of CVE-2026-2703 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-2026-3665](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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2703 and fix it if it is affected.

What it is: CVE-2026-2703 is a medium-severity vulnerability in xlnt-community xlnt, published on 19 Feb 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-2026-2703 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-2026-2703/ (Markdown: https://insights.sbomify.com/CVE-2026-2703/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2703
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2703
- OSV: https://osv.dev/vulnerability/CVE-2026-2703

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2703/
Summaries are generated and may contain mistakes; the official description above is the record.