Vulnerability · Published Oct 14, 2026 · Assigned by VulnCheck

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

Medium 5.5

In plain English

A medium-severity null pointer dereference in xlsxio from brechtsanders. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities).

Severity (CVSS 3.1)5.5Medium

Exploit odds (30 days)0.2%top 85.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
brechtsanders	xlsxio	0 – through 0.2.37

Weakness: CWE-476 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References

https://github.com/brechtsanders/xlsxio/issues/151 issue-tracking
https://github.com/brechtsanders/xlsxio/blob/0.2.37/lib/xlsxio_read.c#L851-L866 technical-description
https://hackmd.io/@haind-pwn/xlsxio-relationship-missing-id-null-deref third-party-advisory
VulnCheck Advisory: xlsxio through 0.2.37 NULL Pointer Dereference via Worksheet Relationship Without Id third-party-advisory