Overview
The cybersecurity world has recently seen the surfacing of a critical vulnerability, CVE-2025-36855, that resides in DiaSymReader.dll. It primarily affects End Of Life (EOL) ASP.NET versions, causing a significant risk to systems running these software components. This vulnerability is of particular concern due to its potential for system compromise or data leakage, making it a significant threat to data security and integrity.
Vulnerability Summary
CVE ID: CVE-2025-36855
Severity: High (CVSS score: 8.8)
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Impact: System compromise or data leakage
Affected Products
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Product | Affected Versions
ASP.NET | 6.0.0 <= 6.0.36 ASP.NET | 8.0.0 <= 8.0.11 ASP.NET | <= 9.0.0 How the Exploit Works
This exploit takes advantage of a buffer over-read in DiaSymReader.dll. A buffer over-read occurs when the system reads from a buffer using access mechanisms such as indexes or pointers that reference memory locations after the buffer. In this case, an attacker can manipulate these mechanisms to read sensitive information from other memory locations, potentially leading to system compromise or data leakage.
Conceptual Example Code
A conceptual example of this vulnerability in action might look something like this:
BufferedStream bs = new BufferedStream(new MemoryStream());
byte[] buffer = new byte[10];
bs.Read(buffer, 11, 2); // Over-readIn this example, the attacker is forcing the system to read beyond the length of the buffer, which can result in unexpected behavior or data leakage.
Impact Summary
The successful exploitation of this vulnerability can lead to severe consequences, including the compromise of the entire system or the leakage of sensitive data. Given the high severity score of 8.8, it is crucial to address this issue urgently.
Mitigation Guidance
As a mitigation strategy, it is recommended to apply the vendor patch. However, if this is not feasible due to the EOL status of the affected software, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation. Furthermore, any self-contained applications targeting the impacted versions are also vulnerable and must be recompiled and redeployed.
Please note that this CVE affects only End Of Life (EOL) software components. The vendor, Microsoft, has indicated there will be no future updates nor support provided upon inquiry. This underscores the importance of keeping software components updated and migrating from EOL versions as soon as possible to maintain a secure and robust system.
