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NVD / CVE Program· CNA ConcreteCMS

CVE-2026-81920: Concrete CMS below 9.5.3 is vulnerable to Cross-Site Request Forgery (CSRF) in Dashboard SEO Excluded Words Reset Endpoint

Noroxi assessment

Priority: Monitor (action score 9/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Concrete CMS below 9.5.3 was vulnerable to Cross-Site Request Forgery in the dashboard SEO Excluded Words page. The reset() controller action cleared the administrator-configured reserved-word list (concrete.seo.exclude_words) but did not validate the anti-CSRF token that the reset modal emitted, and it did not restrict the request to the POST method. A remote attacker who lured an authenticated user with SEO access to a crafted page could revert the reserved-word list to its default and silently alter future URL-slug generation for pages, files, topics, and other objects created through the Text urlify service, undoing the site's configured SEO slug policy. 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:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.

LowCVSS 2.3 · v4.0—No exploit No fix recorded
Published
Sep 15, 2026
Updated
Sep 18, 2026
EPSS
0.1% · 7th percentile

Report tools

JSON

Action score

9

Monitor

Low priority for now.

CVSS
9 / 40 · 2.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · ConcreteCMS
2.3
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-81920

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
concretecmsconcrete cms

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • concretecms concrete cmsbefore 9.5.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (ConcreteCMS). Independent of NVD's CPE analysis and usually ahead of it.

  • Concrete CMS Concrete CMS

    • 5.0.0 and later · up to and including 9.5.2affected · git

Same product

concretecms: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-6826Concrete 9.5.0 and below has file usage disclosure via missing permission check in Usage controller
    60This week
  • CVE-2022-21829Concrete CMS Versions 9.0.0 through 9.0.2 and 8.5.7 and below can download zip files over HTTP and execute code from those zip files which c
    40Plan
  • CVE-2023-48648Concrete CMS before 8.5.13 and 9.x before 9.2.2 allows unauthorized access because directories can be created with insecure permissions.
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-81897Sep 15, 2026 · Concrete CMS below version 9.5.3 is vulnerable to Stored XSS via Express form Text control save_control
    30Monitor
  • ← EarlierCVE-2026-81919Sep 15, 2026 · Concrete CMS below 9.5.3 is vulnerable to Cross-Site Request Forgery (CSRF) in Block Arrangement Endpoint
    9Monitor
  • Later →CVE-2026-81921Sep 15, 2026 · In Concrete CMS 8.5.3 to 9,5,2, OAuth 2.0 Refresh-Token Grant Bypasses Account Status
    9Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-8140117 days apartConcrete CMS 9.5.0 and below is vulnerable to CSRF on download() in the package install controller
    30Monitor
  • CVE-2026-8417117 days apartConcrete CMS 9.5.0 and below is vulnerable to CSRF in do_update() in the package update controller
    30Monitor
  • CVE-2026-8421117 days apartConcrete CMS 9.5.0 and below is vulnerable to CSRF on install_package() with conditional token bypass leading to RCE
    30Monitor
  • CVE-2026-8426117 days apartConcrete CMS 9.5.0 and below is vulnerable to CSRF on prepare_remote_upgrade() leading to one-request RCE via package overwrite
    30Monitor
  • CVE-2026-8428117 days apartCSRF token is not validated in the core CMS update controller for Concrete CMS 9.5.0 and below
    30Monitor
  • CVE-2026-819021 days apartConcrete CMS 9.0.0 to 9.5.2 is vulnerable to CSRF on Orphan Block Cleanup
    28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
P
Scope
X

Weakness class (CWE)

CWE-352 · Cross-Site Request Forgery (CSRF)

CVSS vector

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

nvd-secondary

Root cause

State-changing requests rely on the session cookie the browser sends automatically; nothing verifies that the request came from the user’s own page.

The bug in code

The whole CWE-352 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
app.use(session({ cookie: { httpOnly: true } }));app.post("/account/address", updateAddress);

Fixed

ts
app.use(session({ cookie: { httpOnly: true, sameSite: "lax" } }));app.post("/account/address", csrfProtection, updateAddress);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records