CVE-2026-81910

MEDIUMNVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-09-11. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

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

Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site's publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

CVSS v3
6.5
EG Score
6.5(high)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
16%
KEV
Not listed

Published

September 11, 2026

Last Modified

September 16, 2026

References (1)

Vendor Advisories for CVE-2026-81910(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 20× in last 7d / 24× 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. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 18:37 UTCGHSA enrichment
  3. 2026-09-17 19:42 UTCEG score recompute
  4. 2026-09-17 19:42 UTCGHSA enrichment
  5. 2026-09-16 17:51 UTCEG score recompute▲ 0.60
  6. 2026-09-16 17:51 UTCGHSA enrichment
  7. 2026-09-16 17:41 UTCNVD updateCVSS v3 → 6.5
  8. 2026-09-16 14:08 UTCEPSS rescore
  9. 2026-09-16 13:57 UTCEG score recompute
  10. 2026-09-16 13:57 UTCGHSA enrichment
  11. 2026-09-16 05:15 UTCEPSS rescore
  12. 2026-09-15 15:02 UTCEG score recompute
  13. 2026-09-15 15:02 UTCGHSA enrichment
  14. 2026-09-15 03:12 UTCEPSS rescore
  15. 2026-09-15 03:12 UTCEPSS rescore
  16. 2026-09-14 18:13 UTCGHSA enrichment
  17. 2026-09-13 18:35 UTCEG score recompute
  18. 2026-09-13 18:35 UTCGHSA enrichment
  19. 2026-09-12 19:41 UTCEG score recompute
  20. 2026-09-12 19:41 UTCGHSA enrichment
  21. 2026-09-11 20:46 UTCEG score recompute
  22. 2026-09-11 19:34 UTCEG score recompute
  23. 2026-09-11 18:39 UTCEG score recompute
  24. 2026-09-11 18:38 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-81910?
CVE-2026-81910 is a medium vulnerability published on September 11, 2026. Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and…
When was CVE-2026-81910 disclosed?
CVE-2026-81910 was first published in the National Vulnerability Database on September 11, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-81910 actively exploited?
CVE-2026-81910 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 84.0% of all scored CVEs.
What is the CVSS score of CVE-2026-81910?
CVE-2026-81910 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-81910?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81910, 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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