CVE-2026-100877

MEDIUMPre-NVD 4.34.3—
EchelonGraph scoreHIGH confidence

Score 4.3 from GitHub Security Advisory (severity: LOW) published 2026-09-27. A secondary CVSS source baseline 4.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 5 sources updated this weekElevated
4.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 4.3Exploit: Elevated riskExposed services: Not assessed

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

A vulnerability was determined in mathurvishal CloudClassroom-PHP-Project up to 5dadec098bfbbf3300d60c3494db3fb95b66e7be. Affected by this vulnerability is an unknown functionality of the file registrationform.php. Executing a manipulation of the argument FName/LName/Addrs can lead to cross site scripting. The attack can be executed remotely. The exploit has been publicly disclosed and may be utilized. This product implements a rolling release for ongoing delivery, which means version information for affected or updated releases is unavailable. The vendor was contacted early about this disclosure but did not respond in any way.

CVSS v3
4.3
EG Score
4.3MEDIUMhigh confidence
EG Risk
35
EG Risk 35/100CISA 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
Severity43% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
16th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation public PoC (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

September 27, 2026

Last Modified

September 28, 2026

Advisory Details (1)

Auto-updated Sep 27, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic🟡 PoC Available

Advisory/registrationform-stored-xss.md at main · rmsbpro/Advisory · GitHub

https://github.com/rmsbpro/Advisory/blob/main/registrationform-stored-xss.md

Vendor Advisories for CVE-2026-100877(1)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 26× in last 7d / 26× 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. 2026-10-03 20:55 UTCEG score recompute
  2. 2026-10-03 20:55 UTCGHSA enrichment
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-02 19:56 UTCEG score recompute
  5. 2026-10-02 19:56 UTCGHSA enrichment
  6. 2026-10-01 19:49 UTCEPSS rescore
  7. 2026-10-01 18:56 UTCGHSA enrichment
  8. 2026-09-30 17:56 UTCEG score recompute
  9. 2026-09-30 17:56 UTCGHSA enrichment
  10. 2026-09-30 15:02 UTCEPSS rescore
  11. 2026-09-29 16:46 UTCEG score recompute
  12. 2026-09-29 16:46 UTCGHSA enrichment
  13. 2026-09-29 15:20 UTCEPSS rescore
  14. 2026-09-28 15:29 UTCEG score recompute
  15. 2026-09-28 15:29 UTCGHSA enrichment
  16. 2026-09-28 14:26 UTCEG score recompute
  17. 2026-09-28 14:26 UTCGHSA enrichment
  18. 2026-09-28 14:23 UTCNVD updateCVSS v4 → 2.1
  19. 2026-09-28 14:02 UTCEG score recompute
  20. 2026-09-28 14:02 UTCGHSA enrichment
  21. 2026-09-28 14:01 UTCMITRE cvelistV5CVSS v4 → 5.3
  22. 2026-09-28 13:50 UTCEPSS rescore
  23. 2026-09-27 21:26 UTCEG score recompute
  24. 2026-09-27 21:25 UTCNVD updateCVSS v4 → 2.1
  25. 2026-09-27 20:30 UTCEG score recompute
Show 1 more
  1. 2026-09-27 20:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-100877?
CVE-2026-100877 is a medium vulnerability published on September 27, 2026. A vulnerability was determined in mathurvishal CloudClassroom-PHP-Project up to 5dadec098bfbbf3300d60c3494db3fb95b66e7be. Affected by this vulnerability is an unknown functionality of the file registrationform.php. Executing a manipulation of the argument FName/LName/Addrs can lead to cross site…
When was CVE-2026-100877 disclosed?
CVE-2026-100877 was first published on September 27, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100877 actively exploited?
CVE-2026-100877 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (16th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100877?
CVE-2026-100877 has a CVSS base score of 4.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100877?
No fix for CVE-2026-100877 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-100877 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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