CVE-2026-55085 Etherpad: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in etherpad-lite
An attacker with write access can inject malicious scripts via crafted imports, leading to XSS when other users view the pad.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-55085?
CVE-2026-55085 is a critical cross-site scripting vulnerability in etherpad, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-55085?
How do I fix CVE-2026-55085?
No fix has been published for CVE-2026-55085 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55085 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55085 exists.
Sources
Also known as GHSA-f7h5-v9hm-548j.