CVE-2026-81921

MEDIUMNVD 5.45.4—
EchelonGraph scoreHIGH confidence

Score 5.4 from GitHub Security Advisory (severity: LOW) published 2026-09-15. 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 8.5.3 through 9.5.2 enabled the OAuth 2.0 refresh-token grant using the unmodified upstream League grant, which issued new access tokens from a valid refresh token without re-checking the associated account's active status. A user who obtained a refresh token while active could therefore continue to mint valid access tokens after being deactivated or suspended (uIsActive=0), so deactivating an account did not revoke its API access. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L. Thanks sh4d0byss 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 15, 2026

Last Modified

September 18, 2026

References (1)

Vendor Advisories for CVE-2026-81921(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 / 28× 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. 2026-09-25 05:30 UTCEG score recompute
  2. 2026-09-25 05:30 UTCGHSA enrichment
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-24 03:14 UTCEG score recompute
  5. 2026-09-24 03:14 UTCGHSA enrichment
  6. 2026-09-23 17:54 UTCEPSS rescore
  7. 2026-09-23 00:57 UTCEG score recompute
  8. 2026-09-23 00:57 UTCGHSA enrichment
  9. 2026-09-22 16:01 UTCEPSS rescore
  10. 2026-09-21 22:40 UTCEG score recompute
  11. 2026-09-21 22:40 UTCGHSA enrichment
  12. 2026-09-21 21:09 UTCEPSS rescore
  13. 2026-09-20 20:24 UTCEG score recompute
  14. 2026-09-20 20:24 UTCGHSA enrichment
  15. 2026-09-20 20:16 UTCEPSS rescore
  16. 2026-09-19 18:07 UTCEG score recompute
  17. 2026-09-19 18:07 UTCGHSA enrichment
  18. 2026-09-18 19:28 UTCEPSS rescore
  19. 2026-09-18 15:49 UTCEG score recompute▲ 3.10
  20. 2026-09-18 15:48 UTCGHSA enrichment
  21. 2026-09-18 15:43 UTCNVD updateCVSS v3 → 5.4 · severity → MEDIUM
  22. 2026-09-16 19:23 UTCEG score recompute
  23. 2026-09-16 19:23 UTCGHSA enrichment
  24. 2026-09-16 14:08 UTCEPSS rescore
  25. 2026-09-15 20:41 UTCEG score recompute
Show 3 more
  1. 2026-09-15 19:32 UTCEG score recompute
  2. 2026-09-15 19:00 UTCEG score recompute
  3. 2026-09-15 18:57 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-81921?
CVE-2026-81921 is a medium vulnerability published on September 15, 2026. Concrete CMS 8.5.3 through 9.5.2 enabled the OAuth 2.0 refresh-token grant using the unmodified upstream League grant, which issued new access tokens from a valid refresh token without re-checking the associated account's active status. A user who obtained a refresh token while active could…
When was CVE-2026-81921 disclosed?
CVE-2026-81921 was first published in the National Vulnerability Database on September 15, 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-2026-81921 actively exploited?
CVE-2026-81921 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 86.8% of all scored CVEs.
What is the CVSS score of CVE-2026-81921?
CVE-2026-81921 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-81921?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81921, 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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