Cross-site scripting in Etherpad - CVE-2026-55087
Published: September 22, 2026
Vulnerability identifier: #VU151595
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: CVE-2026-55087
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary JavaScript in an administrator's browser.
The vulnerability exists due to improper neutralization of input during web page generation in the admin static-serving handler when processing an x-proxy-path header in admin HTML, JavaScript, and CSS assets. A remote attacker can send a request with a crafted x-proxy-path header to execute arbitrary JavaScript in an administrator's browser.
User interaction is required, and cache poisoning requires a shared cache that does not vary cached responses by the x-proxy-path header.
Affected software
Etherpad
How to mitigate CVE-2026-55087
Install security update from vendor's website.
Etherpad - update to 3.1.0