Blazor Webassembly application suddenly gives error code: STATUS_ILLEGAL_INSTRUCTION in edge browser

Question

Blazor Webassembly application suddenly gives error code: STATUS_ILLEGAL_INSTRUCTION in edge browser

Evelyn Anyebe (Staff) 60

My blazor webassembly (WASM) application hosted on IIS was running fine but suddenly no longer loads on Microsoft Edge browser.

The edge version is 145.0.3800.82.

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This is happening in the latest Edge release 145.0.3800.82. When I got to edge://settings/privacy/security and disable "Enhance your security on the web" the page loads without an issue. When Enhance your security on the web is enabled and balanced mode selected, the problem occurs. User's image

My WASM app uses .NET 9.0

What could be the cause of this and how do I fix it in my project?

moved from Microsoft Edge | Website issues | Windows 11

Jérôme Lapostolle 20 Reputation points

2026-03-04T12:56:14.9466667+00:00

i am developping a wasm application, it stopped working after the egde update on my company computer. firefox works fine.

it seems any app in blazor is dead, for example the telerik blog on blazor client https://www.telerik.com/blogs/building-interactive-blazor-apps-webassembly is also plagged with the same problem.
Dave Hadner 5 Reputation points

2026-03-05T19:05:48.99+00:00

I recently experienced this issue as well when preparing a new version of an OSS library for release on GitHub and NuGet that includes a demo web app written in C#/WASM/Blazor. Even when running on GitHub pages (e.g., [username].github.io/[projectname]), Edge blocks the WASM app unless you totally turn off security for that site. Quite a bad user experience to see a cryptic "This page is having a problem" and "Error code: STATUS_ILLEGAL_INSTRUCTION" when loading a Microsoft C#/Blazor application in Edge from a Microsoft site using Microsoft tools and runtimes and then telling the user to turn off security for some random [username] that they have never heard of before. I certainly wouldn't do it, and it communicates to the user that they can't trust the OSS library in NuGet or GitHub since Edge detected a potential security issue.

This really needs to be fixed. Works fine in Firefox and Chrome and used to work in Edge. As a former cybersecurity director for a large Fortune 100 company, I get it that reducing the attack surface for WASM is a good thing. But this has the opposite effect because it forces the user to actually turn OFF security checks that they would otherwise have in place but for the WASM attack surface concern.
Evelyn Anyebe (Staff) 60 Reputation points

2026-03-06T01:18:26.4466667+00:00

Thank you for your comment. For me, I have built so much in this app that I need approval to change this app to a use another kind of project. My project manager would not be happy considering the financial implication and time need to rebuild the app. Wouldn't it be better to have mitigations for developers against the WASM attack surface concern
Christensen, Daniel Thomas 25 Reputation points

2026-03-06T14:01:09.0833333+00:00

A temporary solution if your company allows is to add your subdomain to the Edge policy "EnhanceSecurityModeBypassListDomains". Just make sure it is formatted correctly. If your site is https://myproject.mycompany.com/ it needs to be added as "mycompany.com".

Regardless, something has happened from Microsoft's side where EnhanceSecurityMode value 1 now prevents WASM instructions from executing as it is supposed to do in EnhanceSecurityMode value 2. Specifically call "WasmInterpreterRuntime::ClearIndirectCallCacheEntry"
Christensen, Daniel Thomas 25 Reputation points

2026-03-09T06:53:14.53+00:00

A newer Edge update Version 145.0.3800.97 seems to have fixed the problem.

OP, please confirm. I can load all my WASM apps now just fine after getting users to update.

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Jérôme Lapostolle 20 Reputation points

2026-03-04T12:56:14.9466667+00:00

i am developping a wasm application, it stopped working after the egde update on my company computer. firefox works fine.

it seems any app in blazor is dead, for example the telerik blog on blazor client https://www.telerik.com/blogs/building-interactive-blazor-apps-webassembly is also plagged with the same problem.
Dave Hadner 5 Reputation points

2026-03-05T19:05:48.99+00:00

I recently experienced this issue as well when preparing a new version of an OSS library for release on GitHub and NuGet that includes a demo web app written in C#/WASM/Blazor. Even when running on GitHub pages (e.g., [username].github.io/[projectname]), Edge blocks the WASM app unless you totally turn off security for that site. Quite a bad user experience to see a cryptic "This page is having a problem" and "Error code: STATUS_ILLEGAL_INSTRUCTION" when loading a Microsoft C#/Blazor application in Edge from a Microsoft site using Microsoft tools and runtimes and then telling the user to turn off security for some random [username] that they have never heard of before. I certainly wouldn't do it, and it communicates to the user that they can't trust the OSS library in NuGet or GitHub since Edge detected a potential security issue.

This really needs to be fixed. Works fine in Firefox and Chrome and used to work in Edge. As a former cybersecurity director for a large Fortune 100 company, I get it that reducing the attack surface for WASM is a good thing. But this has the opposite effect because it forces the user to actually turn OFF security checks that they would otherwise have in place but for the WASM attack surface concern.
Evelyn Anyebe (Staff) 60 Reputation points

2026-03-06T01:18:26.4466667+00:00

Thank you for your comment. For me, I have built so much in this app that I need approval to change this app to a use another kind of project. My project manager would not be happy considering the financial implication and time need to rebuild the app. Wouldn't it be better to have mitigations for developers against the WASM attack surface concern
Christensen, Daniel Thomas 25 Reputation points

2026-03-06T14:01:09.0833333+00:00

A temporary solution if your company allows is to add your subdomain to the Edge policy "EnhanceSecurityModeBypassListDomains". Just make sure it is formatted correctly. If your site is https://myproject.mycompany.com/ it needs to be added as "mycompany.com".

Regardless, something has happened from Microsoft's side where EnhanceSecurityMode value 1 now prevents WASM instructions from executing as it is supposed to do in EnhanceSecurityMode value 2. Specifically call "WasmInterpreterRuntime::ClearIndirectCallCacheEntry"
Christensen, Daniel Thomas 25 Reputation points

2026-03-09T06:53:14.53+00:00

A newer Edge update Version 145.0.3800.97 seems to have fixed the problem.

OP, please confirm. I can load all my WASM apps now just fine after getting users to update.

Answer 1

Damien Pham (WICLOUD CORPORATION) 1,525 Microsoft External Staff Moderator

Hello @Evelyn Anyebe (Staff) ,

Thank you for reaching out.

I have tested this with the link Jérôme provided above; it works under balanced mode and encounter the same issue under strict mode.

From this document, it is said that "Developers should be aware that the WebAssembly (WASM) interpreter running in enhanced security mode might not yield the expected level of performance. We recommend adding your site as an exception to opt-out of enhanced security mode for site users"

My recommendation is to temporarily disable "Enhance your security on the web" or add your site to exception list
User's image

In case you want this fixed, you can send the feedback by the pressing "ALT+Shift+I" and describe the issue.

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide provide feedback.

Thank you.

Evelyn Anyebe (Staff) 60 Reputation points

2026-03-06T00:28:51.6733333+00:00

Hello,

My website users have limited technology knowledge and Edge browser is the default browser on these PCs. Secondly the PCs are operated in a controlled health environment. I cannot ask them to disable enhanced security setting. The settings can only be done by the health board IT personnel. My website is isolate because it is adapting latest enterprise technology and since other health systems are not experiencing this the IT staff do not want to action my request and think I am at fault.

When I chose Blazor, I thought I was adopting a technology that is modern and will be easily scaled across health board. I am a bit frustrated by Microsoft Edge.
Evelyn Anyebe (Staff) 60 Reputation points

2026-03-06T01:21:43.8333333+00:00

Thank you for pointing ALT+Shift+I. I have sent a feedback describing the issue.
Jérôme Lapostolle 20 Reputation points

2026-03-06T14:35:57.3433333+00:00
do you mean to say that microsoft effectively killed the blazor client technology

by ensuring that it will be hard to use on intranets (good luck changing the security parameters in a corporate environment, or asking security to change the level for localhost urls which are necessary for development)

pretty much made it a no-go for any public-facing site (asking random customers to change advanced browser parameters to accomodate a random website is ludicrous)

the only saving grace on my corporate laptop is that firefox is an alternate allowed browser, but needing to use a conccurent browser to develo on microsoft technology has to be some kind of joke...
Christensen, Daniel Thomas 25 Reputation points

2026-03-06T14:54:05.4633333+00:00

Chrome is also good. Once again, Microsoft proves that Edge shouldn't be taken seriously as an enterprise product.

If Microsoft couldn’t care less and this never gets addressed - another option I am thinking of is running the WASM apps in MAUI while I start to consider permanently abandoning Blazor. But I am unsure if WebView2 instances adopt Edge policies during execution.
Evelyn Anyebe (Staff) 60 Reputation points

2026-03-10T10:52:18.8966667+00:00

The answer is good, it explains the problem and a potential fix. However, it is not correct to ask the end users of my application to change security settings.

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Blazor Webassembly application suddenly gives error code: STATUS_ILLEGAL_INSTRUCTION in edge browser

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