Telerik UI for WinForms: URL Redirection to Untrusted Site
CVE-2026-124700 is a high-severity URL redirection to untrusted site vulnerability in Telerik UI for WinForms from Progress Software, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 2026.4.1111 as the first without the flaw, so updating Telerik UI for WinForms to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.11% 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
- Update Telerik UI for WinForms to 2026.4.1111 or a later version.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Progress Software | Telerik UI for WinForms | 2026.3.1007 up to, but not including, 2026.4.1111 | 2026.4.1111 |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (progress.com).
Official description
In Telerik UI for WinForms, versions prior to 2026.4.1111, an untrusted URL redirection vulnerability exists that allows an attacker to launch arbitrary operating system protocol handlers with attacker-controlled arguments via crafted documents and hyperlinks with a non-allowlisted URI scheme that the user opens.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: URL Redirection to Untrusted Site
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How developers prevent this class of flaw
- Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
- When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to /login.asp and ID 2 could map to http://www.example.com/. Features such as the ESAPI AccessReferenceMap provide this capability.
- Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application. Be sure that the nonce is not predictable (CWE-330).
More URL Redirection to Untrusted Site vulnerabilities (CWE-601)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Telerik UI for WinForms
- 7.8 High severity
- 7.8 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
Recent URL Redirection to Untrusted Site vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 9.6 Critical severity
- 9.0 Critical severity
- 9.6 Critical severity
- 7.5 High severity
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