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TI-2026-39789 Aliases CVE-2026-55085

Etherpad: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in etherpad-lite

Priority HIGH 76CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Cross-site scripting
Confidentiality · integrity · availability
High · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00473 41st percentileScored 2026-11-07
Fix Fixed etherpad (ether): 3.3.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
etheretherpadbefore 3.3.13.3.1Patch availableCNA
  • etherpad Vendorether Affected before 3.3.1 Fixed in 3.3.1 Patch available CNA

Remediation

  • Fix · CNA etherpad (ether) Fixed in 3.3.1

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55085

References

Other 4

  • TI-2026-39793 Etherpad: JWT `admin` claim presence-only check lets non-admin OAuth users invoke every Etherpad HTTP API endpoint CVSS 3.1CRITICAL 9.9
  • TI-2026-39790 Link following in etherpad CVSS 3.1MEDIUM 4.2
  • TI-2009-04910 Session fixation in ether Catalyst::Plugin::Authentication CVSS 3.1CRITICAL 9.1
  • TI-2025-27313 Catalyst::Authentication::Credential::HTTP versions 1.018 and earlier for Perl use insecurely generated nonces CVSS 3.1HIGH 8.6
  • TI-2026-39792 Information disclosure in etherpad CVSS 3.1MEDIUM 6.8
  • TI-2026-39794 Etherpad: Stored XSS in HTML export via unescaped attribute-pool values CVSS 4.0MEDIUM 5.3
See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences