CVE-2026-34943: CWE-248: Uncaught Exception in bytecodealliance wasmtime
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
AI Analysis
Technical Summary
The vulnerability in Wasmtime involves an uncaught panic triggered during the lifting of flags-typed component model values into the Val type when bits outside the defined flags are set. This panic is guest-controlled and can cause a denial-of-service condition in the host environment. The flaw only affects Wasmtime's implementation of lifting into Val and does not impact the flags! macro. It is limited to flags-typed values that are part of a WebAssembly Interface Types (WIT) interface. The issue is addressed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability allows a guest WebAssembly module to cause a panic in the Wasmtime host runtime by providing flags-typed component model values with bits set outside the allowed set. This panic can lead to a denial-of-service condition, disrupting the host's operation. There is no indication of code execution or data breach from this vulnerability. The CVSS 4.0 score is 5.6, indicating a medium severity impact primarily due to potential DoS.
Mitigation Recommendations
The vulnerability is fixed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions or later to remediate the issue. No other mitigation or temporary workaround is indicated in the available data. Patch status is not explicitly confirmed by a vendor advisory but the fixed versions are clearly stated in the description.
CVE-2026-34943: CWE-248: Uncaught Exception in bytecodealliance wasmtime
Description
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in Wasmtime involves an uncaught panic triggered during the lifting of flags-typed component model values into the Val type when bits outside the defined flags are set. This panic is guest-controlled and can cause a denial-of-service condition in the host environment. The flaw only affects Wasmtime's implementation of lifting into Val and does not impact the flags! macro. It is limited to flags-typed values that are part of a WebAssembly Interface Types (WIT) interface. The issue is addressed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability allows a guest WebAssembly module to cause a panic in the Wasmtime host runtime by providing flags-typed component model values with bits set outside the allowed set. This panic can lead to a denial-of-service condition, disrupting the host's operation. There is no indication of code execution or data breach from this vulnerability. The CVSS 4.0 score is 5.6, indicating a medium severity impact primarily due to potential DoS.
Mitigation Recommendations
The vulnerability is fixed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions or later to remediate the issue. No other mitigation or temporary workaround is indicated in the available data. Patch status is not explicitly confirmed by a vendor advisory but the fixed versions are clearly stated in the description.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-31T17:27:08.660Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7f88c1cc7ad14da0c16f4
Added to database: 4/9/2026, 7:05:48 PM
Last enriched: 4/9/2026, 7:22:08 PM
Last updated: 4/10/2026, 8:15:51 AM
Views: 10
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.