Security readout for executives and security teams
Plain-English summary
This issue affects Progress Telerik UI for ASP.NET AJAX RadAsyncUpload. A predictable temporary file identifier may let an attacker cause identifier collisions and tamper with uploaded file content. Business impact is mainly integrity risk in applications using the affected upload control. No active exploitation is indicated in the provided sources.
Executive priority
Treat as a scheduled remediation item, not an emergency based on current evidence. Prioritize systems that accept file uploads from external users, because the main risk is unauthorized alteration of uploaded content.
Technical view
CVE-2026-2878 is CWE-331 insufficient entropy in RadAsyncUpload. Versions prior to 2026.1.225 are described as affected. The temporary identifier is based on timestamp and filename, enabling collisions and potential content tampering. CVSS 3.1 is 5.3 with network attack vector, high attack complexity, no privileges, user interaction required, and high integrity impact.
Likely exposure
Exposure is limited to ASP.NET AJAX applications using Telerik UI RadAsyncUpload on versions before 2026.1.225. Internet-facing upload workflows increase business relevance, but exploitation requires specific conditions and user interaction per the CVSS vector.
Exploitation context
The provided sources do not report public exploitation or CISA KEV listing. The vulnerability is not described as a remote code execution issue. Risk centers on manipulating uploaded content through predictable temporary identifiers under collision conditions.
Researcher notes
Evidence is limited to CVE metadata and the Progress advisory reference. The affected range is stated as prior to 2026.1.225, while the bundled affected entry names 2011.2.712. Validate exact product versions against the vendor advisory before closing exposure.
Mitigation direction
- Upgrade Telerik UI for ASP.NET AJAX to version 2026.1.225 or later.
- Review the Progress vendor advisory for any product-specific configuration guidance.
- Prioritize internet-facing applications using RadAsyncUpload.
- Monitor vendor and CVE records for updated remediation details.
Validation and detection
- Inventory applications using Telerik UI for ASP.NET AJAX.
- Identify whether RadAsyncUpload is enabled or reachable.
- Confirm installed Telerik UI version is 2026.1.225 or later.
- Check upload workflows for exposure to untrusted users.
- Document compensating controls if immediate upgrade is not possible.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-331: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-2878 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N1.63.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.telerik.com/products/aspnet-ajax/documentation/knowledge-base/kb-security-insufficient-entropy-cve-2026-2878CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Insufficient Entropy
Insufficient Entropy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.