CVE-2026-55087

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (45th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 6.1Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
43
EG Risk 43/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity61% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.6%
EPSS %ILE
45th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 13, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Aug 19, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit.
generic

GitHub - ether/etherpad at 3.1.0 · GitHub

https://github.com/ether/etherpad/tree/3.1.0
github_commit Patch Available

commit 8c6104c5d5da (ether/etherpad)

Patch available: ether/etherpad v3.1.0 (contains commit 8c6104c5d5da)

https://github.com/ether/etherpad/commit/8c6104c5d5daf41f0d454acc04d42dffa0e0d996
github_pr Patch Available

harden: assorted server-side tightening for 3.0.2

Patch available: ether/etherpad v3.1.0 (PR #7784 merged 2026-05-17)

https://github.com/ether/etherpad/pull/7784
github Patch Available🟡 PoC Available

x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect) · Advisory · ether/etherpad · GitHub

https://github.com/ether/etherpad/security/advisories/GHSA-fjgc-3mj7-8rg8

Vendor Advisories for CVE-2026-55087(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
ep_etherpad-lite—
  • 2.1.0 up to 3.1.0: fixed in 3.1.0
—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-03 19:50 UTCEG score recompute
  3. 2026-10-03 14:26 UTCEPSS rescore
  4. 2026-10-02 17:56 UTCEPSS rescore
  5. 2026-10-02 07:35 UTCEG score recompute
  6. 2026-10-01 19:50 UTCEPSS rescore
  7. 2026-09-30 21:48 UTCEG score recompute
  8. 2026-09-30 15:03 UTCEPSS rescore
  9. 2026-09-29 15:22 UTCEPSS rescore
  10. 2026-09-28 13:51 UTCEPSS rescore
  11. 2026-09-28 11:17 UTCEG score recompute
  12. 2026-09-27 13:48 UTCEPSS rescore
  13. 2026-09-27 09:45 UTCEG score recompute
  14. 2026-09-26 15:59 UTCEPSS rescore
  15. 2026-09-25 03:34 UTCEG score recompute
  16. 2026-09-24 14:04 UTCEPSS rescore
  17. 2026-09-23 23:32 UTCEG score recompute
  18. 2026-09-23 17:54 UTCEPSS rescore
  19. 2026-09-22 21:26 UTCEG score recompute
  20. 2026-09-21 19:56 UTCEG score recompute
  21. 2026-09-20 20:16 UTCEPSS rescore
  22. 2026-09-20 17:04 UTCEG score recompute
  23. 2026-09-19 15:17 UTCEG score recompute
  24. 2026-09-18 19:28 UTCEPSS rescore
  25. 2026-09-18 13:36 UTCEG score recompute
Show 50 more
  1. 2026-09-17 19:31 UTCEPSS rescore
  2. 2026-09-17 12:05 UTCEG score recompute
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-16 10:33 UTCEG score recompute
  5. 2026-09-16 05:15 UTCEPSS rescore
  6. 2026-09-15 06:58 UTCEG score recompute
  7. 2026-09-15 03:11 UTCEPSS rescore
  8. 2026-09-14 05:28 UTCEG score recompute
  9. 2026-09-13 16:47 UTCEPSS rescore
  10. 2026-09-13 03:58 UTCEG score recompute
  11. 2026-09-12 02:28 UTCEG score recompute
  12. 2026-09-11 14:53 UTCEPSS rescore
  13. 2026-09-11 00:56 UTCEG score recompute
  14. 2026-09-10 09:35 UTCEPSS rescore
  15. 2026-09-09 04:58 UTCEG score recompute
  16. 2026-09-08 22:01 UTCEPSS rescore
  17. 2026-09-07 16:34 UTCEG score recompute
  18. 2026-09-07 16:01 UTCEPSS rescore
  19. 2026-09-06 13:47 UTCEPSS rescore
  20. 2026-09-06 06:21 UTCEG score recompute
  21. 2026-09-05 04:45 UTCEG score recompute
  22. 2026-09-04 05:06 UTCEPSS rescore
  23. 2026-09-03 01:02 UTCEG score recompute
  24. 2026-09-02 14:12 UTCEPSS rescore
  25. 2026-09-01 23:05 UTCEG score recompute
  26. 2026-09-01 13:54 UTCEPSS rescore
  27. 2026-09-01 04:40 UTCEPSS rescore
  28. 2026-08-31 21:34 UTCEG score recompute
  29. 2026-08-30 19:17 UTCEPSS rescore
  30. 2026-08-30 11:56 UTCEG score recompute
  31. 2026-08-30 01:22 UTCEPSS rescore
  32. 2026-08-29 10:22 UTCEG score recompute
  33. 2026-08-28 21:41 UTCEPSS rescore
  34. 2026-08-28 08:51 UTCEG score recompute
  35. 2026-08-27 14:25 UTCEPSS rescore
  36. 2026-08-27 07:18 UTCEG score recompute
  37. 2026-08-26 14:46 UTCEPSS rescore
  38. 2026-08-26 04:27 UTCEG score recompute
  39. 2026-08-25 13:49 UTCEPSS rescore
  40. 2026-08-25 02:57 UTCEG score recompute
  41. 2026-08-24 01:27 UTCEG score recompute
  42. 2026-08-23 00:19 UTCEPSS rescore
  43. 2026-08-22 23:57 UTCEG score recompute
  44. 2026-08-21 23:49 UTCEPSS rescore
  45. 2026-08-21 22:27 UTCEG score recompute
  46. 2026-08-21 22:00 UTCEG score recompute
  47. 2026-08-20 22:55 UTCEPSS rescore
  48. 2026-08-19 20:23 UTCEG score recompute
  49. 2026-08-19 19:34 UTCEG score recompute
  50. 2026-08-13 13:52 UTCEG score recompute

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2026/CVE-2026-55087.yaml
    First seen Jan 1, 2026

    Etherpad 2.1.0 <= 3.0.0 - Cross-Site Scripting

    Open source ↗

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-55087?
CVE-2026-55087 is a medium vulnerability published on August 13, 2026. 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:…
When was CVE-2026-55087 disclosed?
CVE-2026-55087 was first published on August 13, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55087 actively exploited?
CVE-2026-55087 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (45th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55087?
CVE-2026-55087 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55087?
A fix for CVE-2026-55087 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55087 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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