High severity · published Sep 15, 2026
CVE-2026-18424
Concrete CMS 9.0.0 to 9.5.2 is vulnerable to SSRF protection bypass in remote file import when multiple URLs share a host but use different ports
7.1
CVSS
0.2%
EPSS
No
On KEV
Description
Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Server-Side Request Forgery iremote file import via cross-port reuse of a host's validated DNS pin. When multiple remote URLs share the same host, only the first `ValidatedRemoteUrl` is retained and reused for every later URL with that host. A low-privileged authenticated user permitted to import files could therefore supply a DNS-rebinding host that resolved to a public address during validation and to a private or loopback address during the unpinned download, causing the server to fetch internal-only resources such as loopback services, internal admin panels, or cloud metadata endpoints and to save the responses into the file manager. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N. Thanks Ahmad Wicaksono (sonix03) for reporting.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 16% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CC
Concrete CMS · Concrete CMS
9.0.0 through 9.5.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18424
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-18424
Broken Link
https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
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