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CVE-2026-81917

MEDIUM 5.1 ALL-YEARS

Published 2026-09-11 · Last modified 2026-09-14 · ConcreteCMS · NVD: Analyzed

Concrete CMS below 9.5.3 does not apply HTML output escaping to the file description and tags fields when rendering the Document Library block, so a user with permission to edit file properties could store a script payload that executed in the browser of any visitor to a page displaying the block with the description or tags column enabled, including unauthenticated visitors. Successful exploitation could allow theft of session data or actions performed in the visitor's context. The block controller returned the description and tags values without the h() escaping already applied to the title column, and the block view template wrote the returned value directly into the results table The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N. Thanks Nguyen Manh Thuan for reporting.

LIMITED SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.2%chance of exploitation in 30 days · 14th percentile

○ In CISA KEV○ Public exploit / PoC◆ SSVC: exploitation none, automatable no

Impact if exploited

5.1CVSS 4.0 · MEDIUM · CNA

  • ConfidentialityLow
  • IntegrityLow
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires an admin / high-privilege account
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ⚠Requirements: Specific conditions must be present

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

No public exploit or proof-of-concept code is catalogued for this CVE (no ExploitDB, Nuclei, or CISA-KEV entry). It may still exist — search GitHub or check the references below.

Affected

Vendors Concrete Cms Concretecms

Products Concrete Cms

Weakness (CWE)

  • CWE-79: : Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N

Known Affected Software Configurations

VendorProductVersion range
ConcretecmsConcrete Cms< 9.5.3

All CVSS metrics

  • MEDIUM 5.1 v4.0 · CNA Primary
    CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
  • MEDIUM 5.1 v4.0 · NVD Secondary
    CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
  • MEDIUM 5.4 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

References

Patches & mitigations

Sources: NVD · CVE.org · EPSS