bytecodealliance wasmtime up to 24.0.9/36.0.10/44.0.2/45.0.1 File Descriptor fd_renumber release of resource

Summaryinfo

A vulnerability described as problematic has been identified in bytecodealliance wasmtime up to 24.0.9/36.0.10/44.0.2/45.0.1. Impacted is the function fd_renumber of the component File Descriptor Handler. Executing a manipulation can lead to release of resource. This vulnerability appears as CVE-2026-54786. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic was found in bytecodealliance wasmtime up to 24.0.9/36.0.10/44.0.2/45.0.1. This vulnerability affects the function fd_renumber of the component File Descriptor Handler. The manipulation with an unknown input leads to a release of resource vulnerability. The CWE definition for the vulnerability is CWE-772. The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. As an impact it is known to affect availability. CVE summarizes:

Wasmtime is a runtime for WebAssembly. All versions prior to 24.0.10; versions 25.0.0 through those before 36.0.11; versions 37.0.0 through those before 44.0.3; and versions 45.0.0 and 45.0.1 contain a native implementation of WASIp1 which suffers from a leak in the fd_renumber function where the file descriptor being renumbered to is not properly closed. Wasmtime's implementation erroneously only updated the table of descriptors for WASIp1 and didn't update the underlying table of descriptors used by the host. This behavior means that while fd_renumber works correctly from a guest's perspective it ends up leaking resources in the host that aren't cleaned up until the corresponding Store is destroyed. In a loop, guests can use fd_renumber to cause hosts to exhaust both resources and file descriptors. This bug only affects the native implementation of WASIp1, meaning that only runtimes which load core wasm modules and expose fd_renumber are affected. Runtimes are additionally only affected if they expose the ability to acquire a file descriptor, such as opening a file. For runtimes that deny access to files they are unaffected. This issue has been fixed in versions 24.0.10, 36.0.11, 44.0.3, and 45.0.2.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-54786 since 06/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 24.0.10, 36.0.11, 44.0.3 or 45.0.2 eliminates this vulnerability.

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Productinfo

Vendor

• bytecodealliance

Name

• wasmtime

Version

• 24.0.0
• 24.0.1
• 24.0.2
• 24.0.3
• 24.0.4
• 24.0.5
• 24.0.6
• 24.0.7
• 24.0.8
• 24.0.9
• 36.0.0
• 36.0.1
• 36.0.2
• 36.0.3
• 36.0.4
• 36.0.5
• 36.0.6
• 36.0.7
• 36.0.8
• 36.0.9
• 36.0.10
• 44.0.0
• 44.0.1
• 44.0.2
• 45.0.0
• 45.0.1

Website

• Product: https://github.com/bytecodealliance/wasmtime/

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