XSS in Ether Etherpad

CVE-2026-55085

Etherpad is a real-time collaborative editor. Prior to 3.3.1, result.appendSpan in src/static/js/domline.ts interpolates the start attribute of a numbered list directly into an unquoted ol start attribute before assigning the generated markup to node.innerHTML. ImportEtherpad.setPadRaw in src/node/utils/ImportEtherpad.ts accepts attacker-controlled attribute-pool values from a crafted .etherpad import, including list:number1 and a malicious start value. Any user with write access to a pad can store markup that executes as cross-site scripting when another user opens the pad or /timeslider, including when an administrator views the pad. This issue is fixed in version 3.3.1.

Vulnerability class: XSS (Cross-Site Scripting)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L.

EPSS exploit prediction

EPSS: 0.005 (38.7th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 38.7% 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-2026-55085: held from 0.004 to 0.005.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55085?
CVE-2026-55085 is a critical-severity vulnerability in Ether Etherpad, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2026-08-19.
How severe is CVE-2026-55085?
Critical severity. CVSS v3 base score is 9.6 out of 10.