Quick.CMS: Client-Side Enforcement of Server-Side Security
CVE-2026-63301 is a high-severity client-side enforcement of server-side security vulnerability in Quick.CMS from OpenSolution, with a CVSS 4.0 base score of 7.0 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected Quick.CMS versions: 6.8.0 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Quick.CMS you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| OpenSolution | Quick.CMS | 6.8.0 and earlier | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- NoneNo loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- LowLimited loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- NoneNo loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- NoneNo loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- NoneNo loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:L/VA:H/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. Scored by CNA (cert.pl).
Official description
In Quick.CMS, the administrative user interface restricts deletion of the primary language by omitting the corresponding option from the interface; however, the underlying language-deletion API endpoint does not enforce an equivalent server-side authorization check. As a result, an authenticated administrator can bypass the UI-level restriction and delete the primary language by sending a direct HTTP request to the API endpoint. Successful deletion of the primary language results in a Denial of Service (DoS) of application. Critically, when combined with a separate Cross-Site Request Forgery (CSRF) vulnerability (CVE-2026-1468) an unauthenticated remote attacker can craft a malicious link, which if visited by an authenticated administrator, will trigger the DoS condition without direct access to the application The vendor assessed the likelihood of exploitation as very low and determined that a fix is not necessary.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Client-Side Enforcement of Server-Side Security
The product includes a server that relies on the client to implement a protection mechanism that is intended to protect the server.
How developers prevent this class of flaw
- If some degree of trust is required between the two entities, then use integrity checking and strong authentication to ensure that the inputs are coming from a trusted source. Design the product so that this trust is managed in a centralized fashion, especially if there are complex or numerous communication channels, in order to reduce the risks that the implementer will mistakenly omit a check in a single code path.
More Client-Side Enforcement of Server-Side Security vulnerabilities (CWE-602)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Quick.CMS
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
- 8.6 High severity
Recent Client-Side Enforcement of Server-Side Security vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 7.5 High severity
- 7.1 High severity
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