CVE-2026-55087

MEDIUMPre-NVD 6.16.1
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 6.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
Elevated
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 6.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
6.1(low)
EG Risk
48(Track)
EG Risk 48/100SSVC: Track

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%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
45%
KEV
Not listed

Published

August 13, 2026

Last Modified

August 19, 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.

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 3× in last 7d / 4× 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. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-19 20:23 UTCEG score recompute
  3. 2026-08-19 19:34 UTCEG score recompute
  4. 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 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 in the National Vulnerability Database on August 13, 2026, with the most recent update on August 19, 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 1% probability of exploitation in the next 30 days, which ranks it in the top 55.2% of all scored CVEs.
What is the CVSS score of CVE-2026-55087?
CVE-2026-55087 has a CVSS v3 base score of 6.1 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-55087?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55087, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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