VulnerabilityPublished 25 Feb 2026Updated 27 Feb 2026

CVE-2026-2878: Progress Software Telerik UI for ASP.NET AJAX · Insufficient Entropy

Affects Progress Software Telerik UI for ASP.NET AJAXSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 2026.1.225 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2026.1.225

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Progress Software Telerik UI for ASP.NET AJAX to 2026.1.225.

Affected software

Product	Affected	Fixed in
Progress SoftwareTelerik UI for ASP.NET AJAX	Affected >=2011.2.712 <2026.1.225	Fixed in 2026.1.225
NuGettelerik.ui.for.aspnet.ajax`pkg:nuget/telerik.ui.for.aspnet.ajax`Other threats	Affected =2011.2.712	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate this vulnerability, organizations should upgrade Telerik UI for ASP.NET AJAX to version 2026.1.225 or later, where the entropy generation for temporary upload identifiers has been improved to prevent predictability and collisions. If immediate patching is not feasible, implement the following specific mitigations: 1) Customize or override the RadAsyncUpload component to use cryptographically secure random values for temporary file identifiers instead of timestamps and filenames. 2) Implement server-side validation and integrity checks on uploaded files to detect tampering or unexpected modifications. 3) Restrict file upload permissions and isolate upload directories to minimize the impact of potential file overwrites. 4) Monitor upload activity logs for unusual patterns indicative of identifier collision attempts or tampering. 5) Educate users about safe file upload practices to reduce the risk of social engineering attacks requiring user interaction. 6) Employ web application firewalls (WAFs) with rules tuned to detect and block suspicious upload requests targeting RadAsyncUpload endpoints. These targeted mitigations go beyond generic advice by focusing on the specific vulnerability mechanism and its exploitation vectors.

Description

In Progress® Telerik® UI for AJAX, versions prior to 2026.1.225, an insufficient entropy vulnerability exists in RadAsyncUpload, where a predictable temporary identifier, based on timestamp and filename, can enable collisions and file content tampering.

Impact

The primary impact of this vulnerability is on the integrity of uploaded files within web applications using Telerik UI for ASP.NET AJAX. An attacker who can predict temporary upload identifiers may overwrite or tamper with files uploaded by other users, potentially injecting malicious content or corrupting data. This can lead to downstream security issues such as unauthorized code execution if the uploaded files are processed or executed by the server or client. While confidentiality and availability are not directly affected, the integrity compromise can undermine trust in the application and lead to data corruption or exploitation. Organizations relying on Telerik UI for critical business processes or sensitive data handling are at risk of targeted attacks exploiting this flaw. The requirement for user interaction and high attack complexity somewhat limits widespread exploitation but does not eliminate risk, especially in environments with high user traffic or where attackers can trick users into uploading files. The vulnerability could also be leveraged as part of a multi-stage attack chain, increasing its potential impact.

CWE-331Insufficient Entropy (opens in a new tab)
Base weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.
Implementation
Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.
OWASP Cheat Sheets
Session Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
Cryptographic Storage (opens in a new tab)
OWASP ASVS 4.0.3
V3.2.2 (opens in a new tab)
V3.2.4 (opens in a new tab)
V2.3.1 (opens in a new tab)
Attack patterns
Session Credential Falsification through Prediction (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

telerik.com/products/aspnet-ajax/documentation/knowledge-base/kb-security-insufficient-entropy-cve-2026-2878 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Mar 2026, 18:57 UTC

WeaknessesCWE-331

Technical details

References

Community reviews

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