Out-of-bounds Read in Ascensio Onlyoffice Documentserver

CVE-2026-41034

ONLYOFFICE DocumentServer before 9.3.0 has an untrusted pointer dereference in XLS processing/conversion (via pictFmla.cbBufInCtlStm and other vectors), leading to an information leak and ASLR bypass.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.003 (22.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 22nd percentile — 22.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-41034: held from 0.003 to 0.003.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-41034?
CVE-2026-41034 is a medium-severity vulnerability in Ascensio Onlyoffice Documentserver, classified under Out-of-bounds Read. CVSS score: 5.0/10. Published 2026-04-16.
How severe is CVE-2026-41034?
Medium severity. CVSS v3 base score is 5.0 out of 10.