CVE-2026-550876.1MediumCWE-79

CVE-2026-55087: Etherpad: x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect)

ether · etherpad

Affected: etherpad · Exploitation: check available, not yet exploited

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.6%probability of exploitation in the next 30 days

48th percentile

050100

Higher than 48% of scored CVEs

6.1MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

Etherpad is a real-time collaborative editor. From 2.1.0 until 3.1.0, Etherpad uses the attacker-controlled x-proxy-path request header in src/node/hooks/express/admin.ts when substituting paths into HTML, JavaScript, and CSS under /admin without sanitization, Vary: x-proxy-path, or Cache-Control: private, no-store. A shared proxy or CDN can cache the resulting response and serve attacker-injected script to an administrator. In src/node/hooks/express/specialpages.ts, version 3.0.0 also accepts a protocol-relative x-proxy-path value when constructing the /p/:pad/timeslider redirect, allowing redirection to an attacker-controlled host. The issues are exploitable when the deployment permits client-supplied x-proxy-path headers to reach Etherpad. This issue is fixed in version 3.1.0.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

ether · etherpad>= 2.1.0, < 3.1.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Check available, not yet exploited. A public nuclei template can confirm it on a system you are authorised to test.
CISA KEV: Not listed
Public check: Etherpad 2.1.0 <= 3.0.0 - Cross-Site Scripting · nuclei template in projectdiscovery/nuclei-templates
Weakness: Cross-site Scripting
Vendor: ether
Published: August 2026
Band: Check available, not yet exploited, August 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-55087 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.