CVE-2026-81911

MEDIUMNVD 5.45.4—
EchelonGraph scoreHIGH confidence

Score 5.4 from GitHub Security Advisory published 2026-09-11. NVD baseline CVSS 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: None knownExposed: 0

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

Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board's data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.

CVSS v3
5.4
EG Score
5.4(high)
EG Risk
24(Track)
EG Risk 24/100SSVC: 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
Severity54% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

Published

September 11, 2026

Last Modified

September 18, 2026

References (1)

Vendor Advisories for CVE-2026-81911(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 21× in last 7d / 39× 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. 2026-09-24 16:11 UTCEG score recompute
  2. 2026-09-24 16:11 UTCGHSA enrichment
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-23 17:54 UTCEPSS rescore
  5. 2026-09-23 16:41 UTCGHSA enrichment
  6. 2026-09-22 17:11 UTCEG score recompute
  7. 2026-09-22 17:11 UTCGHSA enrichment
  8. 2026-09-22 16:01 UTCEPSS rescore
  9. 2026-09-21 21:09 UTCEPSS rescore
  10. 2026-09-21 17:38 UTCEG score recompute
  11. 2026-09-21 17:38 UTCGHSA enrichment
  12. 2026-09-20 20:16 UTCEPSS rescore
  13. 2026-09-20 18:08 UTCGHSA enrichment
  14. 2026-09-19 18:39 UTCEG score recompute
  15. 2026-09-19 18:39 UTCGHSA enrichment
  16. 2026-09-18 19:28 UTCEPSS rescore
  17. 2026-09-18 19:09 UTCEG score recompute▼ 0.40
  18. 2026-09-18 19:09 UTCGHSA enrichment
  19. 2026-09-18 19:06 UTCNVD updateCVSS v3 → 5.4
  20. 2026-09-18 13:31 UTCEG score recompute
  21. 2026-09-18 13:31 UTCGHSA enrichment
  22. 2026-09-17 14:02 UTCGHSA enrichment
  23. 2026-09-16 14:32 UTCEG score recompute
  24. 2026-09-16 14:32 UTCGHSA enrichment
  25. 2026-09-16 14:08 UTCEPSS rescore
Show 14 more
  1. 2026-09-16 05:15 UTCEPSS rescore
  2. 2026-09-15 15:02 UTCEG score recompute
  3. 2026-09-15 15:02 UTCGHSA enrichment
  4. 2026-09-15 03:12 UTCEPSS rescore
  5. 2026-09-15 03:12 UTCEPSS rescore
  6. 2026-09-14 19:16 UTCGHSA enrichment
  7. 2026-09-13 19:46 UTCEG score recompute
  8. 2026-09-13 19:46 UTCGHSA enrichment
  9. 2026-09-12 20:16 UTCEG score recompute
  10. 2026-09-12 20:16 UTCGHSA enrichment
  11. 2026-09-11 20:46 UTCEG score recompute
  12. 2026-09-11 19:44 UTCEG score recompute
  13. 2026-09-11 19:28 UTCEG score recompute
  14. 2026-09-11 19:28 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-81911?
CVE-2026-81911 is a medium vulnerability published on September 11, 2026. Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The customslot savetemplate endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection]…
When was CVE-2026-81911 disclosed?
CVE-2026-81911 was first published in the National Vulnerability Database on September 11, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-81911 actively exploited?
CVE-2026-81911 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 86.9% of all scored CVEs.
What is the CVSS score of CVE-2026-81911?
CVE-2026-81911 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-81911?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81911, 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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