In the fast-moving world of software development, security holes in frameworks like .NET can have big consequences for developers and businesses. One such vuln was assigned CVE-2022-29117, which targets both .NET and Visual Studio, enabling attackers to cause system slowdowns or outright Denial of Service (DoS). Unlike CVE-2022-23267 and CVE-2022-29145, this vulnerability covers a unique attack surface and set of potential exploit paths.
What is CVE-2022-29117?
CVE-2022-29117 is a Denial of Service (DoS) flaw that affects the .NET runtime, which can be leveraged both by .NET-based applications and by the Visual Studio IDE during builds or related processing.
The root issue:
Attackers can provide specially crafted input (typically large, malformed, or recursive data) that triggers problematic behavior in the .NET runtime, causing the system to hang or consume massive resources. This can prevent applications from functioning or allow an attacker to knock over development and build servers.
Who’s affected?
Technical Details: How the Exploit Works
While Microsoft did not disclose every technical detail, the root cause lies in how the .NET runtime processes regular expressions or data serialization during certain operations. With the right payload, it’s possible to force the .NET runtime into performing excessive computations, leading to a “hang” or resource exhaustion.
Core Example: Regular Expression DoS
One common way to trigger DoS in .NET is through Regex Denial-of-Service (ReDoS), where a regex operation takes exponential time on specific input.
Example vulnerable code
using System.Text.RegularExpressions;
// Vulnerable pattern (catastrophic backtracking possible)
string pattern = @"(a+)+$";
string input = new String('a', 10000) + "!";
Regex regex = new Regex(pattern);
bool isMatch = regex.IsMatch(input);
Console.WriteLine("Match: " + isMatch);
What happens here?
The pattern "(a+)+$" is vulnerable to catastrophic backtracking.
- The input string is very long, and the single '!' at the end will cause the regex engine to backtrack massively.
- This causes the process to consume high CPU for a long time or freeze up, which is the crux of CVE-2022-29117.
With Visual Studio
If a build step or test uses vulnerable code, running the build in Visual Studio can hang or overload the system, affecting developers or build agents.
How Critical is It?
For web-facing applications or any system that processes untrusted user input, DoS flaws like this can make services unreliable. On CI/CD pipelines or shared dev environments, it can easily become a productivity blocker.
- CVSS Score: Microsoft rated this as *Important* (not Critical), but the real-world effect can be pretty disruptive.
Visual Studio updates (varies by edition — install latest updates)
Patch Release Notes: Microsoft Security Update Guide for CVE-2022-29117
> Upgrade your .NET runtime and SDKs!
> These can be updated via Visual Studio Installer or direct downloads (official .NET downloads).
Real-World Attack Example
Suppose you run an ASP.NET Core API. An attacker could POST the crafted string to an endpoint that uses the vulnerable regex. All server threads could become hung, denying service to all other users until the process restarts.
Or, a malicious file could be introduced in a large codebase, and when the CI builds via Visual Studio, the entire pipeline hangs.
Conclusion and Best Practices
CVE-2022-29117 is a silent but nasty DoS bug in modern .NET and Visual Studio. Its simplicity makes it easy to exploit — and easy to avoid with up-to-date systems and some basic coding practices.
Microsoft Security Update Guide:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-29117
.NET Release Notes:
Regex DoS Prevention in .NET:
https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices
Stay secure, keep everything updated, and double-check your regular expressions!
*This in-depth take on CVE-2022-29117 was created exclusively for developers serious about code safety. Share it with your teams and keep hacking (the good way)!*
Timeline
Published on: 05/10/2022 21:15:00 UTC
Last modified on: 05/23/2022 15:59:00 UTC