CVE-2026-62901

Think of your .NET app as following a set of instructions (a loop). This bug lets an attacker feed in weird data so the instructions can repeat far too long (or endlessly), which can freeze or crash the app. The result is downtime—your customers may see errors or timeouts.

This matters if your business runs or builds software using .NET 8.0, .NET 9.0, or .NET 10.0, or you rely on the specific Microsoft Visual Studio 2022/2026 versions listed. Because the issue is reachable over the network with no login and no user action, it’s most relevant for any service that accepts network requests and processes attacker-controlled data.

It’s a risk when an attacker can send data to a network endpoint that your .NET code processes (it’s reachable in default configuration).

Red: attackers can trigger this remotely without logins, and it can stop the .NET system from working via an infinite or excessive loop. That makes it directly useful for causing downtime. Even without confirmed public exploit code, the impact is immediate when the vulnerable code path is reachable over the network, so you should patch on an urgent schedule.

Confirm exposure

1. Identify every place your business uses .NET: production apps, background services, APIs, and any web endpoints.
2. Check the runtime version installed on servers/containers. Also check development/build machines if they deploy artifacts from Visual Studio.
3. Verify whether you have any of the affected versions:
   • .NET 10.0 (needs 10.0.11+)
   • .NET 9.0 (needs 9.0.19+)
   • .NET 8.0 (needs 8.0.30+; this also matches “.net”)
   • Microsoft Visual Studio 2022 version 17.14 (needs 17.14.38+)
   • Microsoft Visual Studio 2026 version 18.8 (needs 18.8.3+)

Patch / upgrade (target fixed versions)

• Upgrade .NET 10.0 to 10.0.11 or later.
• Upgrade .NET 9.0 to 9.0.19 or later.
• Upgrade .NET 8.0 to 8.0.30 or later.
• Upgrade Visual Studio 2022 version 17.14 to 17.14.38 or later.
• Upgrade Visual Studio 2026 version 18.8 to 18.8.3 or later.

Microsoft’s update guidance is here: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62901

Temporary containment (if patching must wait)

• Reduce exposure by limiting which network endpoints accept external requests and ensuring only necessary endpoints are reachable from the internet.
• Add or tighten rate limiting and request size/time limits at the reverse proxy/load balancer (to reduce the chance of a crafted input causing an excessive loop to tie up resources).
• Monitor for service hangs/timeouts and high CPU usage during unexpected request bursts, then block the offending sources if identified.

What to monitor after upgrading

• Application health metrics (availability, response times) for regressions.
• Logs for unusual request patterns or repeated failures from specific IPs.

KEV / deadlines

• This CVE is not listed in CISA KEV in the provided findings, so there is no specific CISA due date mentioned here.

CVE-2026-62901 is a denial-of-service issue (CWE-606) in .NET where specially crafted network input can lead to an excessive or infinite loop due to improper handling of a loop termination condition. The findings state:

• Remote attacker capability over the network
• No authentication required
• No user interaction required
• Reachable in default configuration
• Preconditions: attacker can send data to a network endpoint processed by .NET

Exploit status: no public exploit code was found in the provided findings, and no clearly dated press claim was provided linking this specific CVE to active exploitation. The findings include “press attention” mentioning the patch and an actor name (Lazarus group), but there is no KEV listing and no explicit evidence in the provided data of real-time exploitation.

Fix availability: fixed versions are provided per product branch—.NET 10.0 (10.0.11), .NET 9.0 (9.0.19), .NET 8.0 (8.0.30), and specific Visual Studio versions (17.14.38 and 18.8.3).

KEV meaning (in this case): since it is not in CISA KEV based on the provided findings, there is no mandated “known exploited” indicator from KEV here.